# When does a disease become endemic?

Topics Covered: Issues related to health.

### When does a disease become endemic?

What to study?

For Prelims and Mains: Definition, concerns and ways to address them.

Context: The World Health Organization (WHO) has said that like HIV, the novel coronavirus could become endemic and “may never go away”, and urged for a “massive effort” to contain the spread of COVID-19.

What is an endemic disease?

According to the US Centers for Disease Control and Prevention (CDC), a disease is endemic when its presence or usual prevalence in the population is constant.

In simple terms, an endemic disease is “the constant presence of a disease or infectious agent within a given geographic area or population group; may also refer to the usual prevalence of a given disease within such an area or group.”

Some examples of endemics include the chicken pox and malaria, where there are predictable number of cases every year in certain parts of the world.

What happens when a disease becomes endemic?

When epidemics become endemic, they become “increasingly tolerated” and the responsibility of protecting against it shifts from the government to the individual.

Further, the sociopolitical response to the disease may also change, with investment in the disease becoming institutionalised along with the disease-inducing behavioural changes in people.

Once people become aware of the risks of infection, they will alter their behaviour and mitigate the consequences.

Need for concern:

Epidemic diseases typically have higher mortality and morbidity than endemic diseases, owing to lack of clinical experience and knowledge, as well as innate pathogenicity. Over time, effective prevention and treatment interventions emerge.

When does a disease become endemic?

One mathematical modelling published in the Journal of Epidemiology and Community Health states that if R0, which is the rate at which the virus is transmitted is equal to 1, then the disease is endemic.

When R0>1, it implies that the cases are increasing and that the disease will eventually become an epidemic.

If R0<1, it implies the number of cases of the disease are decreasing.

Here, R0 refers to the number of people infected by a person who has the disease.

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