Public Health & Epidemiology Vocabulary: 100 Key English Terms
Public health professionals use English to read WHO reports and journal articles, write surveillance summaries and project proposals, and work with international partners during outbreaks. This glossary collects the words you meet first: how disease is measured, how outbreaks are detected and controlled, how studies are designed, and how prevention, health promotion and equity are discussed. Each entry explains what the word means, how it is used in real work and how Turkish public health workers say it.
100 terms
10 topics
48 core terms
200 example sentences
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Measuring Health and Disease
epidemiology
noun
Meaning
The study of how often diseases and other health problems occur in different groups of people, why they occur and how they can be controlled.
Where you use it
The core science of public health. A person who does it is an epidemiologist; the adjective is epidemiological (UK) or epidemiologic (US). Common branches include field, infectious disease, chronic disease and social epidemiology.
Examples
We need someone with a background in epidemiology to design the survey.
The epidemiological data point to a link between the water supply and the cases.
Usage note
The main stress falls on 'ol': epi-dee-mee-OL-uh-jee. The same is true of 'epidemiologist'.
Common phrases
field epidemiology · infectious disease epidemiology · epidemiological data · epidemiological study
The number of new cases of a disease in a population during a set period, usually given as a rate such as 25 new cases per 100,000 people per year.
Where you use it
Incidence tells you about risk and how fast a disease is spreading. You speak of the incidence of a disease or an incidence rate, and incidence rises, falls or peaks. Do not mix it up with prevalence, which counts all existing cases.
Examples
The incidence of tuberculosis in the region fell by a third over ten years.
We calculated incidence rates per 100,000 person-years.
Usage note
'Incidence' and 'incidents' (events) sound almost the same. In writing, check which one you mean.
Common phrases
incidence rate · cumulative incidence · annual incidence · high incidence · the incidence of a disease
The proportion of a population that has a disease or condition at a given time, counting both new and existing cases, often given as a percentage.
Where you use it
Prevalence shows how big a problem is and helps plan services. Point prevalence refers to one moment, period prevalence to a span of time. Chronic conditions build up a high prevalence because people live with them for many years.
Examples
In our survey, the prevalence of smoking among adult men was 38 percent.
Hypertension prevalence increases sharply with age.
Usage note
Turkish speakers often write 'prevalance'. The English spelling ends in -ence: prevalence.
Common phrases
high prevalence · point prevalence · prevalence survey · prevalence of obesity · estimated prevalence
The number of deaths in a population during a period, divided by the size of that population, often given per 1,000 or 100,000 people per year.
Where you use it
Also called the death rate. It can be crude (whole population), age-specific or cause-specific, for example the cancer mortality rate. 'Mortality' alone means death in general: 'Mortality from heart disease has fallen.'
Examples
The mortality rate from road traffic injuries is highest among young men.
Crude mortality rates can mislead when two populations have very different age structures.
The state of being ill or having a disease, or the amount of illness in a population, as opposed to mortality, which refers to death.
Where you use it
Usually paired with mortality: morbidity and mortality data, reduce morbidity and mortality. In clinical writing, 'comorbidity' means having another disease at the same time, such as diabetes in a patient with pneumonia.
Examples
Air pollution causes significant morbidity, especially respiratory illness in children.
The programme aims to reduce morbidity and mortality from malaria.
Usage note
In everyday English 'morbid' usually means showing an unhealthy interest in death ('a morbid sense of humour'), but 'morbidity' in health texts simply means illness.
Common phrases
morbidity and mortality · high morbidity · morbidity data · comorbidity
The average number of years a person of a given age can expect to live if current death rates stay the same, most often reported as life expectancy at birth.
Where you use it
One of the most quoted indicators of population health. It rises, falls, stalls or improves, and you compare gaps in life expectancy between countries, regions or income groups. Healthy life expectancy counts only the years lived in good health.
Examples
Life expectancy at birth is several years lower in the poorest districts.
Women's life expectancy is higher than men's in almost every country.
Usage note
Life expectancy at birth is an average that is pulled down by deaths in childhood. It does not mean that most people die at that age.
Common phrases
life expectancy at birth · healthy life expectancy · rise in life expectancy · gap in life expectancy
The proportion of people diagnosed with a disease who die from it, usually within a set time, expressed as a percentage.
Where you use it
Shortened to CFR. It shows how deadly a disease is among known cases, so it looks high when only severe cases are tested. The infection fatality rate (IFR) includes all infections, even undiagnosed ones, and is usually lower.
Examples
The case fatality rate in this outbreak was close to 40 percent.
Early in an epidemic, the case fatality rate is often overestimated.
Usage note
Despite its name, CFR is a proportion, not a true rate, so some textbooks call it the 'case fatality ratio' or 'case fatality risk'. Do not confuse it with the mortality rate, which uses the whole population.
Common phrases
case fatality rate of · high case fatality rate · infection fatality rate · CFR
The number of babies who die before their first birthday for every 1,000 live births in a given year.
Where you use it
One of the most sensitive indicators of a country's overall health and living conditions. It is split into neonatal deaths (first 28 days) and post-neonatal deaths. The under-five mortality rate is a related SDG indicator.
Examples
The infant mortality rate fell sharply after clean water reached the villages.
Infant mortality rates are still twice as high in the eastern districts.
Common phrases
reduce infant mortality · neonatal mortality · under-five mortality · per 1,000 live births
The number of women who die from causes related to pregnancy or childbirth for every 100,000 live births, counting deaths during pregnancy or within 42 days after it ends.
Where you use it
Shortened to MMR, which can be confusing because MMR is also the measles, mumps and rubella vaccine. It is an SDG indicator: the global target is fewer than 70 maternal deaths per 100,000 live births by 2030.
Examples
Training more midwives helped cut the maternal mortality ratio by half in ten years.
The maternal mortality ratio is still far above the SDG target in several countries.
Usage note
It is called a 'ratio' because the denominator is live births, not the number of women.
Common phrases
maternal deaths · reduce maternal mortality · per 100,000 live births · skilled birth attendance
The total impact of a disease or health problem on a population, measured by deaths, illness, disability and sometimes economic cost.
Where you use it
The Global Burden of Disease (GBD) study compares conditions and risk factors across countries using DALYs. People speak of a high or growing burden, the burden of mental illness and reducing the disease burden.
Examples
Depression accounts for a large share of the burden of disease among young adults.
The report estimates the burden of disease caused by air pollution in each province.
Common phrases
global burden of disease · disease burden · high burden · reduce the burden
The number of deaths from all causes during a period above what would normally be expected, based on earlier years.
Where you use it
Widely used during heatwaves and the COVID-19 pandemic because it captures deaths that were never tested or correctly recorded. Analysts estimate excess deaths by comparing observed deaths with expected deaths.
Examples
The heatwave was followed by clear excess mortality among people over 75.
Excess mortality figures suggest that the official death toll was too low.
Short for disability-adjusted life year: one year of healthy life lost, either through early death or through living with illness or disability.
Where you use it
DALYs are the sum of years of life lost (YLL) and years lived with disability (YLD). They are the main unit of the Global Burden of Disease study and let very different problems, such as road injuries and depression, be compared. Often read aloud as 'dally'.
Examples
Low back pain causes millions of DALYs every year even though it rarely kills.
The programme costs about 50 dollars per DALY averted.
Usage note
A related measure, the QALY (quality-adjusted life year), counts healthy years gained rather than lost and is used more in health economics.
Common phrases
DALYs averted · DALYs lost · cost per DALY · years lived with disability
A rate adjusted to remove the effect of differences in age structure, so that populations with more older or more younger people can be fairly compared.
Where you use it
Calculated with a standard population, such as the WHO or European standard population. Reports compare age-standardized mortality or incidence rates between countries, regions and years. British spelling: age-standardised. Also called an age-adjusted rate.
Examples
The crude cancer death rate rose, but the age-standardized rate actually fell.
We compared age-standardized rates of stroke across the seven regions.
Common phrases
age-standardized mortality rate · standard population · crude rate · age-adjusted rate
An observational study that follows a group of people over time, comparing those with and without an exposure to see who develops a disease or outcome.
Where you use it
Can be prospective (following people forward from now) or retrospective (using records from the past). Cohort studies measure incidence and relative risk directly, but large ones are slow and expensive. Participants are recruited and followed up.
Examples
In this cohort study, 12,000 nurses were followed for twenty years.
A birth cohort study can show how early-life conditions affect adult health.
Common phrases
prospective cohort study · retrospective cohort study · birth cohort · follow up a cohort · loss to follow-up
An observational study that starts with people who have a disease (cases) and people who do not (controls), then looks back to compare their past exposures.
Where you use it
Popular for rare diseases and outbreak investigations because it is quick and cheap. Results are usually expressed as an odds ratio. Choosing suitable controls and avoiding recall bias are the main challenges.
Examples
A case-control study linked the outbreak to a salad served at the wedding.
For the case-control study, each case was matched to two controls of the same age and sex.
Common phrases
matched case-control study · conduct a case-control study · cases and controls · recall bias
A study in which participants are assigned by chance to receive an intervention or a comparison, such as a placebo or usual care, so that the outcomes of the groups can be fairly compared.
Where you use it
Usually shortened to RCT and seen as the strongest single design for testing whether an intervention works. In public health, whole villages, schools or clinics may be randomized instead of individuals; this is a cluster randomized trial.
Examples
A randomized controlled trial showed that text message reminders improved vaccine uptake.
Not every public health question can be answered with a randomized controlled trial.
Usage note
British English spells it 'randomised'. Both spellings are correct; follow the style of the journal or organisation you write for.
Common phrases
conduct a randomized controlled trial · cluster randomized trial · double-blind trial · control group · RCT evidence
A study that collects information from a population at one point in time, like a snapshot, to measure how common a disease, behaviour or exposure is.
Where you use it
Most health surveys are cross-sectional and report prevalence. Because exposure and outcome are measured at the same time, these studies cannot show which came first, so they are weak at proving cause.
Examples
We carried out a cross-sectional study of 3,000 households in rural areas.
This cross-sectional study cannot tell us whether stress causes poor sleep or the other way round.
Common phrases
cross-sectional survey · cross-sectional design · cross-sectional data · carry out a cross-sectional study
A study in which researchers observe and measure people's exposures and outcomes without assigning any treatment or intervention themselves.
Where you use it
Cohort, case-control, cross-sectional and ecological studies are all observational. They are often the only ethical or practical choice, but they are more open to confounding than trials, so results are described as associations.
Examples
This is an observational study, so it cannot prove that the diet prevents dementia.
Large observational studies first raised concerns about the drug's safety.
Common phrases
observational data · observational evidence · large observational study · ecological study
A review that uses a clear, pre-planned method to find, select and assess all the relevant studies on a specific question and then combine their findings.
Where you use it
Placed near the top of the evidence hierarchy and used to write guidelines. Authors register a protocol, search databases, screen studies and assess risk of bias. Many systematic reviews include a meta-analysis, but not all.
Examples
The guideline is based on a systematic review of school-based physical activity programmes.
Two reviewers independently screened the studies for the systematic review.
Usage note
A 'narrative review' simply summarises the literature without a strict, reproducible method; a systematic review must report exactly how studies were found and chosen.
Common phrases
conduct a systematic review · systematic review and meta-analysis · review protocol · evidence synthesis
A statistical method that combines the numerical results of several similar studies to produce one overall estimate of an effect.
Where you use it
Usually part of a systematic review. Results are shown in a forest plot with a pooled estimate and confidence interval. Researchers check heterogeneity, meaning how much the studies differ. The plural is meta-analyses.
Examples
The meta-analysis pooled data from twelve trials with over 30,000 participants.
Because the studies were so different, the authors decided not to do a meta-analysis.
Common phrases
systematic review and meta-analysis · pooled estimate · forest plot · heterogeneity
A characteristic, behaviour or exposure that increases the chance of developing a disease or health problem, such as smoking, high blood pressure or poor housing.
Where you use it
Central to chronic disease work. Some risk factors are modifiable (diet, alcohol, inactivity) and some are not (age, sex, family history). Researchers identify risk factors and programmes target them. The opposite is a protective factor.
Examples
Smoking remains the most important preventable risk factor for lung cancer.
We looked for risk factors associated with severe illness in older adults.
Usage note
A risk factor is linked to higher risk; it is not necessarily the cause. Use 'for' with the disease: 'a risk factor for stroke'.
Common phrases
modifiable risk factor · major risk factor · behavioural risk factors · identify risk factors · a risk factor for
Contact with or experience of something that may affect health, such as a germ, a chemical, tobacco smoke, a type of diet or a particular job.
Where you use it
In study design, the exposure is the factor being studied and the outcome is the disease. People are exposed to something; you measure the level, length or route of exposure. In outbreaks, a 'high-risk exposure' is close unprotected contact with a case.
Examples
Long-term exposure to fine particulate matter is linked to heart disease.
Health workers who reported a needle-stick exposure were offered testing.
Common phrases
occupational exposure · exposure to · level of exposure · high-risk exposure · exposure and outcome
A systematic error in how a study is designed, carried out or analysed that pushes its results away from the truth in one direction.
Where you use it
Every study is checked for bias. Common types are selection bias, information or measurement bias and recall bias. You avoid, reduce, introduce or assess bias, and a result can be biased. Bias is different from random error, which more data can reduce.
Examples
Self-reported weight introduces bias because people tend to underestimate it.
The reviewers judged most of the studies to be at high risk of bias.
Usage note
In everyday English 'bias' also means prejudice against a group. In research it is a technical word for systematic error, with no moral judgement.
A distortion that happens when a third factor is linked to both the exposure and the outcome, making their relationship look stronger, weaker or different than it really is.
Where you use it
The factor itself is called a confounder or confounding variable. Researchers control or adjust for confounding through study design, such as randomization and matching, or in the analysis. Age and smoking are classic confounders.
Examples
Coffee drinking appeared to be linked to lung cancer until the analysis adjusted for confounding by smoking.
Residual confounding may explain part of the association.
Usage note
In everyday English 'confound' means to confuse or surprise someone; in research it has this narrow technical meaning.
Common phrases
adjust for confounding · residual confounding · confounding variable · confounding factor · control for confounders
The risk of an outcome in an exposed group divided by the risk in an unexposed group; a value of 2 means the exposed group has twice the risk.
Where you use it
Also called the risk ratio (RR) and calculated in cohort studies and trials. A value of 1 means no difference; below 1 suggests a protective effect. Absolute risk should be reported too, because a doubled risk of a very rare event is still small.
Examples
In our cohort, night-shift workers had a relative risk of 1.4 for type 2 diabetes.
The headline said the risk had doubled, but the relative risk hid a tiny absolute difference.
Common phrases
relative risk of · risk ratio · absolute risk · relative risk reduction
A measure of association that compares the odds of an exposure among cases with the odds among controls, or the odds of an outcome in two groups.
Where you use it
Shortened to OR and the standard measure in case-control studies and logistic regression. An OR of 1 means no association; above 1 means higher odds, below 1 lower odds. When the outcome is rare, the OR is close to the relative risk.
Examples
Eating at the buffet was strongly associated with illness, with an odds ratio of 4.2.
The adjusted odds ratio was 1.8 (95% CI 1.3 to 2.5).
Usage note
'Odds' and 'probability' are not the same: a probability of 0.2 equals odds of 0.25 (1 to 4). That is why many Turkish texts keep the English word 'odds'.
Common phrases
adjusted odds ratio · crude odds ratio · an odds ratio of · calculate an odds ratio
A range of values around an estimate that shows how precise it is; a 95% confidence interval is calculated so that, if a study were repeated many times, 95% of such intervals would contain the true value.
Where you use it
Written 95% CI and read 'ninety-five percent confidence interval'. A narrow interval means a precise estimate. If the CI for a relative risk or odds ratio includes 1, the result is usually not statistically significant.
Examples
Prevalence was 12.4% (95% confidence interval 10.9 to 13.9).
The confidence interval is very wide because the sample was small.
Common phrases
95% confidence interval · narrow confidence interval · wide confidence interval · the confidence interval includes 1
Bias that occurs when the people included in a study, or those who stay in it, differ systematically from the population the results are meant to describe.
Where you use it
Examples include the healthy worker effect, volunteer bias and loss to follow-up. Researchers try to minimise selection bias through random sampling, high response rates and careful choice of controls.
Examples
An online survey about exercise may suffer from selection bias, since active people are more likely to reply.
Hospital-based controls can introduce selection bias into a case-control study.
A statistical link between an exposure and an outcome, meaning they occur together more or less often than chance would predict, whether or not one causes the other.
Where you use it
Researchers find, observe or report an association, then judge whether it is causal using criteria such as strength, consistency, timing and dose-response, often called the Bradford Hill criteria. 'Association is not causation' is a common warning.
Examples
We found a strong association between poor housing and childhood asthma.
The association disappeared after we adjusted for income.
Usage note
Say 'an association between A and B' or 'A is associated with B'; avoid 'associated to'.
Common phrases
strong association · causal association · association between · dose-response relationship
A sudden rise in the number of cases of a disease above what is normally expected, usually limited to one place, group or event.
Where you use it
The everyday word in outbreak work. An outbreak occurs or breaks out; teams detect, investigate, contain and finally declare an outbreak over. Officials often prefer 'outbreak' to 'epidemic' because it sounds smaller and less alarming.
Examples
A norovirus outbreak on the cruise ship affected over 200 passengers.
The team was sent to investigate a measles outbreak in a primary school.
Usage note
The verb is 'break out' (two words) and the noun is 'outbreak' (one word): 'Cholera broke out', but 'a cholera outbreak'.
Common phrases
outbreak investigation · contain an outbreak · foodborne outbreak · declare an outbreak over · outbreak response
A rise in cases of a disease well above the expected level in a population or region, usually spreading more widely than an outbreak.
Where you use it
Used for infectious diseases (a cholera epidemic) and also for non-infectious problems that grow alarmingly, such as the obesity epidemic or the opioid epidemic. It also works as an adjective: epidemic levels.
Examples
The country declared a dengue epidemic after cases tripled in a month.
Experts warn that type 2 diabetes is reaching epidemic levels.
Usage note
The 'epidemic curve' (epi curve) is a graph of cases by date of symptom onset, one of the first things drawn in an outbreak investigation.
An epidemic that spreads across several countries or continents and affects a very large number of people.
Where you use it
Mostly used for new infections that spread worldwide, such as the influenza pandemics of 1918 and 2009 or COVID-19. People talk about pandemic preparedness, the pandemic response and life before and after the pandemic.
Examples
Every country needs an up-to-date pandemic preparedness plan.
During the pandemic, many routine vaccination services were disrupted.
Usage note
'Pandemic' describes how widely a disease spreads, not how severe it is.
Common phrases
pandemic preparedness · global pandemic · influenza pandemic · pandemic response · during the pandemic
The passing of an infection from one person, animal or source to another, for example through the air, by touch, through food and water or by insects.
Where you use it
Described by route: airborne, droplet, contact, foodborne, waterborne, vector-borne or mother-to-child transmission. You reduce, interrupt or break the chain of transmission. 'Community transmission' means new cases cannot be linked to a known source.
Examples
Hand washing is one of the simplest ways to reduce transmission.
There is now evidence of community transmission in three provinces.
Usage note
The verb is 'transmit': 'The virus is transmitted by mosquitoes.' Do not use 'transfer' for infections.
Common phrases
community transmission · airborne transmission · chain of transmission · mother-to-child transmission · reduce transmission
Finding and contacting people who have been near an infected person, so they can be informed, tested, watched for symptoms or asked to stay at home.
Where you use it
Used for tuberculosis, sexually transmitted infections, measles and, most famously, COVID-19. Contact tracers interview the case, list close contacts and follow them up. You do, carry out or scale up contact tracing.
Examples
Contact tracing identified 43 close contacts of the first patient.
We need more staff to keep up with contact tracing as cases rise.
Usage note
The Turkish word 'filyasyon' comes from French 'filiation'. English 'filiation' does not have this meaning, so always say 'contact tracing'.
Common phrases
contact tracing team · close contact · carry out contact tracing · trace contacts · contact tracing app
Separating and restricting the movement of people who may have been exposed to an infection but are not sick, to see whether they become ill.
Where you use it
Usually lasts as long as the incubation period. People are put in, placed under or released from quarantine, and 'quarantine' is also a verb. In everyday speech it is used loosely for any stay-at-home rule, but public health staff keep it separate from isolation.
Examples
Close contacts were asked to quarantine at home for 21 days.
The crew remained in quarantine on board until the test results came back.
Usage note
Quarantine is for people who may be infected; isolation is for people who are known to be infected. Turkish speakers often use 'karantina' for both.
Common phrases
in quarantine · home quarantine · quarantine period · be placed under quarantine · lift a quarantine
Keeping people who are sick or known to be infected away from others, at home or in a health facility, to stop the infection spreading.
Where you use it
Common in hospitals (isolation room, isolation ward) and in outbreak guidance (self-isolation). People isolate, self-isolate or are placed in isolation, and isolation ends when they are no longer infectious.
Examples
The patient with suspected TB was moved to an isolation room.
Strict isolation of cases helped bring the outbreak under control.
The time between being infected with a disease and the first appearance of symptoms.
Where you use it
Usually given as a range and a median, for example 'two to fourteen days'. It decides how long quarantine and contact follow-up last and helps outbreak teams work out when people were exposed.
Examples
Measles has an incubation period of about ten to twelve days before the fever starts.
Because of the long incubation period, cases kept appearing weeks after the event.
Usage note
The 'latent period' is different: it is the time until a person becomes infectious, which can be shorter than the incubation period.
Common phrases
average incubation period · short incubation period · median incubation period · within the incubation period
An illness caused by a microorganism, such as a virus, bacterium or parasite, that can pass from one person or animal to another.
Where you use it
The usual term in public health agencies and laws: communicable disease control, communicable disease surveillance. 'Infectious disease' is very close in meaning and more common in clinical medicine. The opposite is a noncommunicable disease.
Examples
She leads the communicable disease team at the provincial health directorate.
Communicable diseases still cause many deaths among young children in poorer countries.
Usage note
'Contagious' is narrower and more everyday: it describes diseases that spread easily from person to person, such as measles or chickenpox.
Common phrases
communicable disease control · communicable disease surveillance · communicable disease team · infectious disease
Describes a disease that is always present in a particular area or population at a fairly constant, expected level.
Where you use it
A disease is endemic in a region, and a new infection may become endemic after a pandemic. Endemic does not mean harmless or rare: an endemic disease can still cause many deaths. The noun is endemicity.
Examples
Malaria is endemic in many parts of sub-Saharan Africa.
Crimean-Congo haemorrhagic fever is endemic in several provinces of Türkiye.
Usage note
For diseases, say 'endemic in a country'. 'Endemic to' is mostly used in biology for plants and animals found only in one place.
Common phrases
endemic disease · endemic area · endemic in · become endemic · endemic transmission
The average number of people one infected person would pass the infection to in a population where nobody is immune. It is written R0 and read 'R nought' or 'R zero'.
Where you use it
If R0 is above 1, an infection can spread; below 1, it dies out. Measles has one of the highest values, often quoted as 12 to 18. The effective reproduction number (Rt or Re) reflects immunity and control measures at a given time.
Examples
The basic reproduction number of measles is much higher than that of seasonal flu.
Models suggest the basic reproduction number for this strain is around 2.5.
Usage note
'Nought' is British for zero; Americans usually say 'R naught' or 'R zero'. Turkish texts often simply write 'R0' or 'R sayısı'.
Common phrases
estimate the basic reproduction number · R nought · effective reproduction number · keep R below 1
The proportion of people at risk who become ill during an outbreak or another short, defined period, usually given as a percentage.
Where you use it
Used in outbreak investigations to compare groups, for example people who ate a certain dish and people who did not. The secondary attack rate is the proportion of contacts, such as household members, who catch the infection from a case.
Examples
The attack rate among guests who ate the chicken was 62 percent.
Household secondary attack rates were higher for the new variant.
Usage note
Despite the name, it is a proportion (a form of cumulative incidence), not a rate over time.
The first case of a disease that comes to the attention of health authorities in an outbreak or a family, leading investigators to look for others.
Where you use it
Investigators interview the index case to find contacts and the likely source. The index case is not always the first person infected; that person is called the primary case. The media often use the phrase 'patient zero'.
Examples
The index case was a nurse who had returned from a conference abroad.
All household contacts of the index case were tested.
Usage note
Public health professionals avoid 'patient zero' in formal writing because it can blame or stigmatise one person.
Common phrases
identify the index case · primary case · patient zero · contacts of the index case
A group of cases that occur closer together in time or place than would be expected, which may or may not turn out to share a common cause.
Where you use it
Agencies investigate clusters of cancer, birth defects or infection, and a cluster can grow into an outbreak. As a verb, cases cluster in a school or an area. In study design, a cluster randomized trial assigns whole groups rather than individuals.
Examples
A cluster of Legionnaires' disease was linked to a hotel cooling tower.
Cases seem to cluster around the new factory, so we have started an investigation.
Having an infection or a disease without showing any of its symptoms.
Where you use it
Asymptomatic infections matter because people may spread disease without knowing it. Related words are presymptomatic (before symptoms start) and mild. An asymptomatic carrier can sometimes pass on an infection for a long time.
Examples
Many children with the infection are completely asymptomatic.
Screening showed that a third of positive cases were asymptomatic at the time of testing.
An infectious disease that passes from animals to humans, such as rabies, brucellosis or avian influenza.
Where you use it
The plural is zoonoses and the adjective is zoonotic. Most new infectious diseases are zoonotic, which is why human, animal and environmental health are increasingly managed together under the One Health approach.
Examples
Brucellosis is a zoonosis often linked to unpasteurised milk and cheese.
Veterinary and human health services should share data on emerging zoonoses.
A living creature, such as a mosquito, tick or sandfly, that carries an infection from one person or animal to another.
Where you use it
Malaria, dengue, Lyme disease and Crimean-Congo haemorrhagic fever are vector-borne diseases. Programmes focus on vector control: removing breeding sites, using bed nets and spraying insecticide.
Examples
The tiger mosquito is a vector for dengue and chikungunya.
Warmer winters are helping the vector spread to new regions.
Usage note
In maths and computing 'vector' has other meanings; in public health it almost always means an animal that carries disease.
The continuous, systematic collection, analysis and interpretation of health data, shared in good time so that action can be taken to prevent and control disease.
Where you use it
A key word in every public health agency. Passive surveillance relies on routine reports from doctors and labs; active surveillance means staff go out and look for cases. You set up, strengthen or carry out surveillance, and a disease can be under surveillance.
Examples
Surveillance data showed flu activity rising two weeks earlier than usual.
The ministry is strengthening surveillance of antimicrobial resistance in hospitals.
Usage note
In everyday English 'surveillance' often means watching people for security reasons. In public health it means watching diseases and health trends, not spying on individuals.
Common phrases
disease surveillance · active surveillance · passive surveillance · surveillance system · surveillance data
A person in a population or study who has the disease, infection or condition being investigated, usually decided by agreed criteria.
Where you use it
Epidemiologists count cases, not patients. Cases are classified as suspected, probable or confirmed, and can be new, imported, locally acquired or fatal. Reports talk about case numbers, case counts and rising cases.
Examples
We have three confirmed cases and five suspected cases so far.
Case numbers usually peak in late January.
Usage note
'A case of measles' means one person with measles, not a box or a legal case. In clinical settings people say 'patient'; in surveillance they say 'case'.
Common phrases
confirmed case · suspected case · probable case · imported case · case count
A standard set of criteria, such as symptoms, lab results, time and place, used to decide whether a person should be counted as a case of a particular disease.
Where you use it
Essential for comparable surveillance data and outbreak investigations. Case definitions often have levels (suspected, probable, confirmed). Teams agree on, apply, update or widen a case definition; a broad one finds more cases but is less precise.
Examples
Our case definition was anyone with diarrhoea who ate at the restaurant between 3 and 5 May.
When the case definition changed, the number of reported cases jumped.
Common phrases
standard case definition · surveillance case definition · apply a case definition · broaden the case definition
A disease that doctors and laboratories are required by law to report to public health authorities whenever they diagnose or suspect it.
Where you use it
Each country keeps its own list. British English prefers 'notifiable disease'; American texts often say 'reportable disease'. A case is notified or reported; some diseases must be reported immediately, others within a few days.
Examples
Measles is a notifiable disease, so the clinic informed the health directorate the same day.
The list of notifiable diseases was updated to include mpox.
Common phrases
notifiable disease list · notify a case · reportable disease · statutory notification
The situation when the number of cases or deaths reported to health authorities is lower than the true number, for example because people do not seek care or doctors do not notify.
Where you use it
A known weakness of passive surveillance. Analysts estimate the level of underreporting and may apply a correction factor. Also written under-reporting; the verb is underreport and the adjective underreported.
Examples
Underreporting of foodborne illness is common because most people never see a doctor.
We believe the official figures hide serious underreporting in rural areas.
Common phrases
underreporting of cases · level of underreporting · correct for underreporting · underreported cases
An organised system that collects standard information on every person with a particular disease in a defined population, often over many years.
Where you use it
Cancer registries are the best-known example; there are also registries for birth defects, stroke and rare diseases. Data are entered, linked and validated, and the registry provides incidence and survival figures for research and planning.
Examples
According to the regional disease registry, childhood leukaemia rates have been stable.
Hospitals send every new diagnosis to the disease registry within three months.
Usage note
'Registry' and 'register' are both used in British English; American English mostly uses 'registry'.
Common phrases
cancer registry · population-based registry · registry data · rare disease registry
Surveillance based on a selected group of reporting sites, such as certain clinics or laboratories, that collect high-quality data to follow trends rather than count every case.
Where you use it
Widely used for influenza and other respiratory viruses, where selected family practices take swabs from a sample of patients. The chosen locations are called sentinel sites. It is cheaper than covering the whole population but may not represent every group.
Examples
Sentinel surveillance showed that RSV activity started earlier this autumn.
Twenty family practices take part in our sentinel surveillance network.
Surveillance that tracks groups of symptoms or other health-related signals, such as fever and cough, before a lab diagnosis is made, in order to detect unusual activity early.
Where you use it
Uses near real-time data from emergency departments, telephone helplines, pharmacy sales or school absences. It gives early warning of outbreaks, heatwave effects or problems at mass gatherings, but its signals must be confirmed by other methods.
Examples
Syndromic surveillance picked up a rise in gastrointestinal illness two days after the flood.
During the festival, we ran daily syndromic surveillance in all emergency departments.
Common phrases
syndromic surveillance system · early warning · real-time data · signal detection
Giving a vaccine to a person so that their immune system learns to protect them against a specific infectious disease.
Where you use it
Used for single doses and for whole programmes: routine childhood vaccination, a vaccination campaign. WHO documents often use 'immunization' in the same sense. People get vaccinated; health workers vaccinate people or give a vaccine.
Examples
Measles vaccination rates dropped in several districts last year.
The vaccination campaign targets all children under five.
Usage note
'Vaccine' is the product; 'vaccination' is the act of giving it. Say 'the vaccine is safe' and 'vaccination is free', not the other way round.
Common phrases
routine vaccination · vaccination campaign · vaccination programme · get vaccinated · mass vaccination
Indirect protection that happens when enough people in a community are immune to an infection, so it cannot spread easily and even unprotected people are less likely to catch it.
Where you use it
Discussed with vaccination targets. The herd immunity threshold depends on how contagious the disease is: for measles it is around 95 percent. Also called community immunity or population immunity, terms many health agencies now prefer.
Examples
Babies too young to be vaccinated rely on herd immunity for protection.
If coverage falls below 95 percent, herd immunity against measles may be lost.
Common phrases
herd immunity threshold · achieve herd immunity · community immunity · population immunity
Action taken to stop a disease or injury from happening at all, for example vaccination, seat belt laws or reducing the salt in processed food.
Where you use it
The first of the three levels of prevention (primary, secondary, tertiary). It acts on healthy people before any disease begins and is often the most cost-effective. Some texts add primordial prevention, which tackles the conditions that create risk factors.
Examples
Adding fluoride to drinking water is a classic example of primary prevention.
Most of our budget still goes on treatment rather than primary prevention.
Usage note
The usual adjective is 'preventive' (preventive medicine, preventive services); 'preventative' is also correct but less formal.
Common phrases
primary prevention programme · focus on primary prevention · levels of prevention · primordial prevention
Testing people who have no symptoms to find a disease or its early signs, so that it can be treated earlier and more successfully.
Where you use it
Examples include cervical, breast and bowel cancer screening and newborn screening. People are invited for, offered or attend screening; programmes are judged by uptake, accuracy and harms such as overdiagnosis.
Examples
Only half of eligible women attended breast screening last year.
Newborn screening can detect several rare conditions in the first days of life.
Usage note
A screening test is not a diagnosis: a positive result usually needs a further diagnostic test.
Common phrases
screening programme · cancer screening · screening test · screening uptake · population screening
Finding a disease early, before or soon after symptoms begin, and acting quickly to stop it from getting worse, for example through screening.
Where you use it
The second level of prevention, mainly about early detection and prompt treatment. Cancer screening, blood pressure checks and testing for hepatitis C are typical. In cardiology the phrase also means preventing a second heart attack or stroke.
Examples
Regular eye checks for people with diabetes are a form of secondary prevention.
Funding for secondary prevention was cut, so fewer cancers were caught early.
Common phrases
secondary prevention programme · early detection · prompt treatment · secondary prevention of stroke
Reducing the impact of an illness that people already have, by preventing complications, disability and relapse and helping them live as well as possible.
Where you use it
The third level of prevention. Cardiac rehabilitation, diabetic foot care and support groups after a stroke are typical examples. It overlaps with clinical care and rehabilitation services.
Examples
Tertiary prevention in diabetes focuses on avoiding amputations and kidney failure.
Rehabilitation after a heart attack is a classic example of tertiary prevention.
A delay in accepting, or a refusal of, vaccines even when vaccination services are available, often driven by doubts, mistrust or misinformation.
Where you use it
WHO listed it among the ten threats to global health in 2019. Experts talk about addressing, tackling or understanding vaccine hesitancy and stress that hesitant parents are not the same as committed anti-vaccine activists.
Examples
Vaccine hesitancy among young parents has grown since the pandemic.
Family doctors are often the best people to address vaccine hesitancy.
The percentage of people in a target group who have received a particular vaccine or all the required doses, such as children who had two doses of measles vaccine by age two.
Where you use it
A core indicator for immunization programmes, also written vaccine coverage or immunization coverage. Coverage can be high, low, falling or patchy, and is reported nationally and by district. 'Uptake' is a near-synonym used in the UK.
Examples
Vaccination coverage for the first measles dose fell below 90 percent in some districts.
We mapped vaccination coverage to find pockets of unvaccinated children.
An extra dose of a vaccine given some time after the first doses to restore or strengthen protection that has faded over time.
Where you use it
Often simply called a booster. Many countries give tetanus and diphtheria boosters at set intervals, and COVID-19 boosters became widely known. People get, receive or are offered a booster dose; waning immunity is the usual reason for one.
Examples
Older adults were offered a booster dose before winter.
Protection wanes after a few years, so a booster dose is needed.
Usage note
Turkish 'rapel' comes from French 'rappel'. In English, say 'booster', never 'rappel'.
The system of storing and transporting vaccines and some medicines at the correct low temperature, usually between 2 and 8°C, from the factory until they are used.
Where you use it
A weak cold chain can make vaccines useless. Staff monitor temperatures with data loggers, record any break in the cold chain and report a cold chain failure. Some vaccines need ultra-cold storage.
Examples
A power cut broke the cold chain, and 200 doses had to be thrown away.
Solar refrigerators have improved the cold chain in remote clinics.
Common phrases
maintain the cold chain · break in the cold chain · cold chain equipment · cold chain failure
Permanently reducing the worldwide incidence of an infection to zero, so that control measures are no longer needed anywhere.
Where you use it
Smallpox, declared eradicated in 1980, is the only human disease eradicated so far; polio is close. 'Elimination' is narrower: stopping transmission in one country or region, as many countries have done with measles or malaria.
Examples
The global eradication of smallpox is often called the greatest achievement of public health.
The polio eradication programme now focuses on the last few places where the wild virus circulates.
Usage note
Eradication is worldwide and permanent; elimination applies to a defined area. Learners often use the two words as synonyms.
The official timetable that sets which vaccines people should receive, at what ages and in how many doses, in a particular country.
Where you use it
Also called a vaccination schedule. National committees review and update it when new vaccines appear. Children are up to date with or behind on their vaccines, and catch-up vaccination is offered to those who missed doses. UK spelling: immunisation schedule.
Examples
The hepatitis A vaccine was added to the national immunization schedule.
Migrant children often need a catch-up plan to complete the immunization schedule.
Common phrases
national immunization schedule · routine immunization · catch-up vaccination · up to date with vaccines
The process of enabling people and communities to increase control over their health and improve it, through education, supportive environments, healthy policies and community action.
Where you use it
The idea was shaped by WHO's Ottawa Charter for Health Promotion (1986). It covers much more than leaflets: workplace wellness schemes, smoke-free laws and healthy school meals all count. You work in, plan or deliver health promotion.
Examples
The city's health promotion team runs walking groups in every district.
Schools are one of the best settings for health promotion.
Common phrases
health promotion campaign · health promotion programme · workplace health promotion · health promotion specialist
A planned action, programme or policy designed to improve health or change a health-related behaviour or condition in a group of people.
Where you use it
Anything from a sugar tax to a school handwashing project can be an intervention. Researchers design, implement, scale up and evaluate interventions and compare an intervention group with a control group. Non-pharmaceutical interventions (NPIs) include masks and school closures.
Examples
The intervention reduced smoking among pregnant women by 15 percent.
We need evidence that the intervention is cost-effective before we scale it up.
Usage note
In Turkish 'müdahale' can sound forceful or medical; in English public health writing 'intervention' is neutral and can mean any planned programme.
Common phrases
public health intervention · evaluate an intervention · intervention group · non-pharmaceutical interventions · scale up an intervention
The ability to find, understand, judge and use health information to make decisions about one's own health and health care.
Where you use it
Low health literacy is linked to poorer health and more hospital visits. Organisations measure, improve or take account of health literacy, for example by using plain language and checking understanding. Digital health literacy covers online information.
Examples
Leaflets should be written for readers with limited health literacy.
The survey found low health literacy in nearly half of older adults.
Common phrases
low health literacy · limited health literacy · improve health literacy · digital health literacy · plain language
The process of people adopting healthier habits or giving up harmful ones, and the methods used to help them, such as information, support, incentives and changes to their surroundings.
Where you use it
Used for smoking, diet, exercise, handwashing and much more. Programmes are based on behaviour change theories and techniques; 'nudges' are small changes to the way choices are presented that make the healthy option easier. American spelling: behavior change.
Examples
Information alone rarely leads to lasting behaviour change.
The campaign used behaviour change techniques such as goal setting and reminders.
Usage note
British 'behaviour' and American 'behavior' are both correct; keep to one spelling throughout a document.
An approach that aims to reduce the health and social harms of risky behaviours, such as drug use, without requiring people to stop the behaviour completely.
Where you use it
Classic examples are needle and syringe programmes, opioid substitution therapy and naloxone distribution. It is now also discussed for alcohol and tobacco. People speak of harm reduction services, strategies and approaches.
Examples
Needle exchange is a harm reduction measure that has lowered HIV infections among people who inject drugs.
The city opened its first harm reduction centre last year.
Usage note
Public health texts prefer person-first language such as 'people who use drugs' rather than labels like 'drug addicts'.
Common phrases
harm reduction services · harm reduction approach · needle and syringe programme · people who use drugs
The real-time exchange of information, advice and opinions between experts, officials and the public about a health threat, so that people can make informed decisions to protect themselves.
Where you use it
A core part of emergency response, often paired with community engagement (RCCE). Good risk communication is early, honest and consistent and admits uncertainty. Teams also track and respond to rumours and misinformation.
Examples
Poor risk communication in the first week led to panic buying.
Our risk communication strategy relies on local radio and trusted community leaders.
Common phrases
risk communication strategy · crisis communication · tackle misinformation · communicate uncertainty
Planned learning activities that give people the knowledge, skills and motivation to make healthier choices, for example lessons, workshops, counselling or leaflets.
Where you use it
A key tool of health promotion, but narrower: it informs and motivates, while health promotion also changes environments and policies. Health education is delivered in schools, clinics and workplaces and through the media.
Examples
The nurses run health education sessions on breastfeeding for new mothers.
Health education in schools covers hand hygiene, nutrition and dental care.
Common phrases
health education programme · school health education · deliver health education · health education materials
Working with communities as partners, so that local people help to identify problems and plan, deliver and evaluate the health programmes that affect them.
Where you use it
Seen as essential for building trust, especially in outbreaks and vaccination campaigns. Programmes involve community health workers, local leaders and youth groups. Related terms include community participation and co-production.
Examples
Strong community engagement helped end the Ebola outbreak in the district.
Community engagement starts with listening, not with telling people what to do.
Common phrases
community engagement strategy · community health workers · engage communities · community participation
The set of policies and programmes that aim to reduce tobacco use and exposure to tobacco smoke, such as taxes, smoke-free laws, warning labels and support to quit.
Where you use it
Guided internationally by the WHO Framework Convention on Tobacco Control (FCTC), adopted in 2003. WHO's MPOWER package summarises the main measures. Raising tobacco taxes is considered one of the most effective tobacco control tools.
Examples
The country strengthened tobacco control by raising taxes and banning advertising.
She has worked in tobacco control for twenty years.
The conditions in which people are born, grow, live, work and age, such as income, education, housing and employment, which strongly shape their health.
Where you use it
A central idea in modern public health and WHO policy. People address, tackle or act on the social determinants of health; American texts often use the short form SDOH. A related phrase is 'the causes of the causes'.
Examples
You cannot reduce childhood asthma without looking at social determinants of health such as damp housing.
The new strategy asks every ministry to act on the social determinants of health.
Usage note
'Determinants' is plural here; one factor is 'a social determinant of health'.
Common phrases
address the social determinants of health · act on the social determinants · structural determinants · commercial determinants of health
The situation in which everyone has a fair chance to be as healthy as possible, with no avoidable or unfair differences in health between social groups.
Where you use it
A goal, a value and a way of looking at policy. Agencies promote, advance or achieve health equity and carry out health equity assessments. Its opposite, health inequity, means differences that are unfair and avoidable, not simply unequal.
Examples
Health equity should be built into every stage of programme design.
The report treats access to clean water as a health equity issue.
Usage note
Equality means giving everyone the same; equity means giving people what they need to reach the same level of health. Learners often mix the two words up.
Common phrases
promote health equity · achieve health equity · health equity lens · health equity impact assessment
A person's or group's position in society based on a combination of income, education and occupation, often used to compare health between social groups.
Where you use it
Shortened to SES. Studies adjust for SES or compare people of low and high SES. It is measured with indicators such as income, years of schooling, occupational class or area deprivation indices.
Examples
Children from families with low socioeconomic status had more tooth decay.
We adjusted the model for age, sex and socioeconomic status.
Common phrases
low socioeconomic status · high socioeconomic status · adjust for socioeconomic status · socioeconomic position · deprivation index
Differences in health, such as life expectancy or disease rates, between groups of people defined by income, area, ethnicity, gender or other social factors.
Where you use it
The usual British term; American texts often say 'health disparities'. Policies aim to reduce, tackle or narrow health inequalities. Many writers keep the word 'inequities' for differences that are unfair and avoidable.
Examples
Health inequalities between the richest and poorest areas have widened over the past decade.
Reducing health inequalities is one of the five aims of the strategy.
Common phrases
reduce health inequalities · tackle health inequalities · widening health inequalities · health disparities
The ability of people to get the health services they need when they need them, which depends on cost, distance, waiting times, language and whether the services exist at all.
Where you use it
Used in debates about rural areas, migrants, people with disabilities and costs. Barriers to access can be financial, geographical, cultural or administrative. Also written 'access to health care' or simply 'access to care'.
Examples
Women in remote villages have poor access to healthcare during pregnancy.
Mobile clinics were set up to improve access to healthcare for seasonal farm workers.
Usage note
The noun takes 'to': 'access to healthcare', not 'access of healthcare'. The verb takes no preposition: 'access services'.
Common phrases
barriers to access · improve access to healthcare · unequal access · access to care
Groups of people who face a higher risk of poor health or have more difficulty getting care, for example because of age, poverty, disability, migration status or homelessness.
Where you use it
Common in plans and reports: protect, reach or prioritise vulnerable groups. Many writers now prefer 'groups made vulnerable' or 'underserved populations' to show that vulnerability comes from circumstances, not from the people themselves.
Examples
The heat health plan prioritises vulnerable groups such as older people living alone.
Outreach teams visit vulnerable groups who rarely use health services.
Common phrases
protect vulnerable groups · hard-to-reach groups · underserved populations · vulnerable populations
Lack of reliable access to enough affordable, safe and nutritious food for an active and healthy life, often because of low income.
Where you use it
Measured with household surveys and graded as mild, moderate or severe. Food insecurity is linked to both undernutrition and obesity. Do not confuse it with food safety, which is about contamination.
Examples
One in five households in the survey reported food insecurity.
Rising prices pushed many families into severe food insecurity.
Usage note
Turkish 'gıda güvenliği' can mean both 'food security' (having enough food) and 'food safety' (food free from contamination); English keeps the two apart.
Common phrases
household food insecurity · severe food insecurity · food security · food bank
The pattern in which health gets steadily better at each step up the social ladder, so that not only the poorest but everyone below the top has worse health than those above them.
Where you use it
Made famous by the Whitehall studies of British civil servants and the work of Michael Marmot. Researchers describe a steep or shallow social gradient in health. 'Proportionate universalism' is the idea of acting across the whole gradient, with more effort where need is greater.
Examples
The data show a clear social gradient in childhood obesity across all five income groups.
Policies aimed only at the poorest will not flatten the social gradient.
Common phrases
social gradient in health · steep social gradient · proportionate universalism · flatten the gradient
The branch of public health that deals with how the physical environment, including air, water, food, housing, noise and chemicals, affects people's health.
Where you use it
Environmental health officers inspect restaurants, investigate noise and housing complaints and check water quality. The field increasingly covers climate change, heat and extreme weather.
Examples
Environmental health officers closed the restaurant after finding rats in the kitchen.
Climate change is now a central issue in environmental health.
Common phrases
environmental health officer · environmental health risks · environmental hazards · environmental exposure
Harmful substances in the air, such as fine particles, nitrogen dioxide and ozone, that come from traffic, industry, heating and the burning of fuels and damage health.
Where you use it
WHO counts it among the biggest environmental risks to health, linked to stroke, heart disease, lung cancer and respiratory illness. People talk about outdoor (ambient) and household air pollution, PM2.5 levels and air quality guidelines.
Examples
Air pollution levels in the city exceeded WHO guideline values on most winter days.
Children living near busy roads are more exposed to air pollution.
Common phrases
air quality · household air pollution · PM2.5 levels · exposure to air pollution · reduce air pollution
Short for water, sanitation and hygiene: safe drinking water, toilets and the safe disposal of human waste, and handwashing, treated together as one area of public health.
Where you use it
Pronounced like the word 'wash'. Common in humanitarian and development work and in assessments of schools and health facilities. Poor WASH conditions spread diarrhoea, cholera and other infections. SDG 6 sets the global targets.
Examples
The camp's WASH team installed new latrines and handwashing stations.
Improving WASH in schools reduced absences caused by diarrhoea.
Usage note
In English 'sanitation' means toilets, sewage and waste systems, not general cleaning. For cleaning, say 'cleaning' or 'disinfection'.
Common phrases
WASH programme · safe drinking water · sanitation facilities · hand hygiene
The field that protects and promotes the health of workers by preventing work-related illness and injury and making workplaces safer and healthier.
Where you use it
Covers hazards such as dust, noise, chemicals, heavy lifting, shift work and stress. Usually paired with safety: occupational health and safety (OHS or OSH). Occupational health doctors and nurses carry out health surveillance of workers.
Examples
The occupational health team found high levels of silica dust at the quarry.
Night-shift nurses with sleep problems were referred to occupational health.
Common phrases
occupational health and safety · occupational disease · occupational exposure · workplace hazards
An approach that recognises that the health of people, animals and the environment is closely connected and brings these sectors together to prevent and control health threats.
Where you use it
Applied to zoonoses, antimicrobial resistance and food safety. Doctors, vets, ecologists and agriculture experts share data and plan together. It is promoted jointly by FAO, UNEP, WHO and WOAH, a partnership known as the Quadripartite.
Examples
A One Health approach brought vets and doctors together to tackle the rabies cases.
Antimicrobial resistance cannot be solved without One Health thinking.
Usage note
Written with capital letters as a proper name: 'One Health', not 'one health'.
Common phrases
One Health approach · One Health framework · human, animal and environmental health · cross-sector collaboration
The science and practice of protecting and improving the health of whole populations through prevention, education, policy and organised community action, rather than by treating individual patients.
Where you use it
Used for the field, the profession and the goal. You work in public health or study it, often for an MPH (Master of Public Health). It also works like an adjective: a public health problem, public health measures, a public health emergency.
Examples
She left clinical work after ten years and moved into public health.
Childhood obesity is now treated as a major public health problem.
Usage note
As the name of a field it takes no article: 'She works in public health', not 'in the public health'.
Common phrases
public health problem · public health measures · public health emergency · work in public health · Master of Public Health (MPH)
Short for the World Health Organization, the United Nations agency for international public health, founded in 1948 and based in Geneva.
Where you use it
WHO sets global norms and guidelines, coordinates the response to health emergencies and publishes data and fact sheets used everywhere in public health. Its decision-making body is the World Health Assembly. It has six regional offices; Türkiye is in the European Region.
Examples
The figures come from the latest WHO report on tuberculosis.
Our ministry is working with WHO on a national plan for antimicrobial resistance.
Usage note
Say the letters W-H-O, not the word 'who'. WHO itself writes the name without an article ('WHO recommends'), although 'the WHO' is common in the media. The official name uses the spelling 'Organization'.
Common phrases
WHO guidelines · WHO recommendations · WHO member states · WHO regional office · WHO fact sheet
A long-lasting illness that is not passed from person to person, such as heart disease, cancer, chronic lung disease or diabetes.
Where you use it
Usually shortened to NCD. NCDs cause most deaths worldwide, and WHO names their main risk factors as tobacco use, harmful use of alcohol, unhealthy diet and physical inactivity, with air pollution often added. Also spelled non-communicable.
Examples
Noncommunicable diseases now account for most deaths in middle-income countries.
The plan sets targets for reducing premature deaths from noncommunicable diseases.
Common phrases
NCD prevention · burden of noncommunicable diseases · premature deaths from NCDs · NCD risk factors
A situation in which everyone can use the good-quality health services they need, from prevention to treatment and care, without suffering financial hardship.
Where you use it
Shortened to UHC and part of the Sustainable Development Goals (target 3.8). Countries move towards, achieve or expand UHC. Discussions focus on service coverage, financial protection and out-of-pocket spending.
Examples
Universal health coverage means a farmer should not have to sell land to pay a hospital bill.
The ministry presented its roadmap towards universal health coverage.
Common phrases
achieve universal health coverage · progress towards UHC · financial protection · out-of-pocket spending
Essential, community-based health care that is people's first point of contact with the health system, covering prevention, treatment of common conditions and health promotion close to where they live.
Where you use it
Set out as a goal for all countries in the Declaration of Alma-Ata (1978) and renewed in the Astana Declaration (2018). Shortened to PHC. 'Primary care' usually refers more narrowly to services given by family doctors and nurses.
Examples
Strong primary health care can meet most people's health needs close to home.
The country invested in primary health care instead of building more hospitals.
Common phrases
primary health care services · strengthen primary health care · primary care · Declaration of Alma-Ata
All the organisations, people, resources and actions whose main purpose is to promote, restore or maintain health in a country, including financing, workforce, services and governance.
Where you use it
WHO describes six building blocks: service delivery, health workforce, information, medical products, financing, and leadership and governance. People strengthen, reform or overload a health system; 'health systems strengthening' is a common goal.
Examples
The pandemic exposed weaknesses in the health system, especially staff shortages.
A resilient health system can keep routine services running during a crisis.
Usage note
'Health care system' and 'healthcare system' are also common; 'health system' is the usual term in WHO documents.
Common phrases
health system strengthening · resilient health system · health system reform · health system capacity
A legally binding international agreement that sets out how countries and WHO must detect, report and respond to public health risks that may spread across borders.
Where you use it
Usually written IHR or IHR (2005), after the year of the current version. Each country has a National IHR Focal Point that communicates with WHO, and countries assess their core capacities for surveillance, laboratories and points of entry such as airports.
Examples
Under the International Health Regulations, the event had to be reported to WHO within 24 hours of assessment.
The airport's health unit was upgraded to meet the International Health Regulations.
Common phrases
IHR (2005) · National IHR Focal Point · core capacities · points of entry
An extraordinary event that WHO formally declares because it is a public health risk to other countries through international spread and may need a coordinated international response.
Where you use it
Shortened to PHEIC and often pronounced 'fake'. The WHO Director-General declares it on the advice of an Emergency Committee under the IHR. Examples include H1N1 influenza in 2009, Zika in 2016, COVID-19 in 2020 and mpox in 2022 and 2024.
Examples
WHO declared COVID-19 a public health emergency of international concern in January 2020.
The Emergency Committee met to decide whether the event was a public health emergency of international concern.
Common phrases
declare a PHEIC · Emergency Committee · temporary recommendations · end a PHEIC
The ability of bacteria, viruses, fungi and parasites to survive medicines that used to kill them, making infections harder or impossible to treat.
Where you use it
Shortened to AMR. It is driven by the overuse and misuse of antimicrobials in people, animals and farming, and is tackled through surveillance, infection control and antimicrobial stewardship programmes. 'Antibiotic resistance' is the narrower term for bacteria.
Examples
Antimicrobial resistance threatens to make routine surgery much riskier.
The national action plan on antimicrobial resistance covers both hospitals and farms.
Common phrases
tackle antimicrobial resistance · antibiotic resistance · antimicrobial stewardship · drug-resistant infections · national action plan on AMR
Countries classified by the World Bank as having low, lower-middle or upper-middle income per person, a grouping widely used in global health research and funding.
Where you use it
Shortened to LMICs. The term has largely replaced older labels such as 'developing countries' or 'the Third World'. The World Bank updates its classification every year, so a country can move from one group to another.
Examples
Most deaths from cervical cancer now occur in low- and middle-income countries.
The grant supports researchers based in low- and middle-income countries.
Usage note
Note the hyphen in 'low- and middle-income': it shows that 'low' also goes with 'income'.
Common phrases
LMICs · high-income countries · resource-limited settings · Global South
Seventeen global goals adopted by all UN member states in 2015 to end poverty, protect the planet and improve lives by 2030; Goal 3 is about health and well-being.
Where you use it
Shortened to SDGs; single goals are called SDG 3, SDG 6 and so on, each with targets and indicators, such as 3.1 on maternal mortality and 3.8 on universal health coverage. Health appears in many goals, not only SDG 3.
Examples
The country is not on track to meet the Sustainable Development Goals on child mortality.
Our project contributes to several Sustainable Development Goals, including clean water and gender equality.
Common phrases
SDG 3 · SDG targets · SDG indicators · 2030 Agenda · on track to meet the SDGs
Short for the Centers for Disease Control and Prevention, the national public health agency of the United States, based in Atlanta.
Where you use it
Its guidance, data and training materials are read around the world. Other agencies use similar names, such as the ECDC (European Centre for Disease Prevention and Control) in Stockholm and Africa CDC. Both 'CDC' and 'the CDC' are used.
Examples
We used the CDC case definition so that our data would be comparable.
The ECDC and the CDC both published risk assessments on the new variant.
Usage note
The abbreviation stayed CDC, not CDCP, even after 'and Prevention' was added to the name in 1992.
Ten questions from this glossary. Pick the right meaning for each term and see your score.
How to learn public health & epidemiology vocabulary
Learn the key measures and concepts in pairs and make sure you can explain each difference in one sentence: incidence and prevalence, quarantine and isolation, relative risk and odds ratio, eradication and elimination.
Read real public health texts in English every week, such as WHO fact sheets and outbreak news, national surveillance reports and abstracts in public health journals, and notice how numbers and uncertainty are described.
Practise saying numbers aloud: '12.4 per 100,000 population', 'an odds ratio of 1.8, 95% confidence interval 1.3 to 2.5'. Presentations and team meetings are full of them.
Learn the verbs that go with each noun: detect and contain an outbreak, notify a case, trace contacts, scale up an intervention, adjust for confounding.
Watch the words that Turkish uses differently, such as 'filyasyon' (contact tracing), 'rapel' (booster dose), 'vaka' and 'olgu' (both 'case') and 'gıda güvenliği', which can mean either food security or food safety.
Frequently asked questions
What is the difference between incidence and prevalence?
Incidence counts new cases during a period and tells you about risk and how fast a disease is spreading. Prevalence counts everyone who has the condition at a given time, both new and old cases, and tells you how big the problem is. A disease that people live with for years, such as diabetes, can have a high prevalence even when relatively few new cases appear each year.
Outbreak, epidemic and pandemic: what is the difference?
All three describe more cases than expected. An outbreak is usually limited to one place or group, such as a school or a town; an epidemic covers a wider area or population; a pandemic spreads across several countries or continents. The boundaries are not strict, and officials often prefer 'outbreak' because it sounds less alarming. Turkish uses 'salgın' for all three, with 'epidemi' and 'pandemi' for the larger ones.
Should I say 'case' or 'patient' in epidemiology?
In epidemiology and surveillance, say 'case': a confirmed case, case numbers, case definition. Use 'patient' when you talk about someone receiving care from a health worker. In Turkish, academic texts prefer 'olgu' and the media 'vaka'; both translate 'case'.
Should I use British or American spelling in public health writing?
Both are accepted; what matters is consistency within a document. American texts write behavior, randomized and immunization; British texts write behaviour and randomised, and often immunisation. WHO documents generally use British spelling with -ize endings, as in 'behaviour' and 'immunization'. Follow the style guide of the journal or organisation you are writing for.
How do I read rates such as '25 per 100,000' aloud?
Say 'twenty-five per hundred thousand' or 'twenty-five per one hundred thousand population'. Rates are usually given per 1,000 (births and infant deaths), per 100,000 (incidence and mortality) or as percentages (prevalence and coverage). Remember that English uses a point for decimals and a comma for thousands, 12.5 and 100,000, which is the opposite of Turkish 12,5 and 100.000.
