Disease Becoming Endemic

18 May 2020

According to the World Health Organization (WHO), 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?

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 numbers 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.
This means, rather than government agencies actively engaging in tracking and identifying cases, the individuals themselves will be responsible for managing risk from the disease and seeking care.
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.

Types of Endemic Diseases

Holoendemic Diseases: This infection is highly prevalent in the early years of life. The adult population does not show traces of diseases as much as children do. This kind of endemic disease affects mostly children .E.g. Malaria

Hyperendemic Diseases: These types of endemic diseases are constantly present at a high rate and are found among all age groups equally. E.g. Chicken Pox.

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.

What is the concern about an epidemic?

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.

Epidemic vs. Pandemic

A simple way to know the difference between an epidemic and a pandemic is to remember the “P” in pandemic, which means a pandemic has a passport.
A pandemic is an epidemic that travels.

Epidemic vs. Endemic

An epidemic is actively spreading; new cases of the disease substantially exceed what is expected. More broadly, it’s used to describe any problem that’s out of control, such as “the opioid epidemic.”
An epidemic is often localized to a region, but the number of those infected in that region is significantly higher than normal.
For example, when COVID-19 was limited to Wuhan, China, it was an epidemic. The geographical spread turned it into a pandemic.
Endemics, on the other hand, are a constant presence in a specific location.
Malaria is endemic to parts of Africa.
Ice is endemic to Antarctica.

Endemic vs. Outbreak

Going one step farther, an endemic can lead to an outbreak, and an outbreak can happen anywhere.
2019 dengue fever outbreak in Hawaii is as an example. Dengue fever is endemic to certain regions of Africa, Central and South America, and the Caribbean.
Mosquitoes in these areas carry dengue fever and transmit it from person to person. But in 2019 there was an outbreak of dengue fever in Hawaii, where the disease is not endemic.
It’s believed an infected person visited the Big Island and was bitten by mosquitoes there.
The insects then transferred the disease to other individuals they bit, which created an outbreak.