COVID In India May Enter Endemic Stage: What Is An Endemic? Endemic Vs Epidemic Vs Pandemic

What Is An Endemic?

By definition, an endemic means something that is 'natural to, native to, confined to, or widespread within' a place or population of people [2]. Endemic can be a disease that is prevalent in or restricted to a particular location, region, or population; a disease present permanently in a region or population.

For example, chickenpox, malaria etc., are endemic diseases, and these are relatively rare and not as widespread as an epidemic [3]. An endemic continues to exist in the population that lives in that area and is caused by viruses, bacteria, or parasites that can transmit diseases to humans [4].

Endemic diseases are of two types [5]:

(1) Holoendemic diseases: A disease is defined as holoendemic when every individual in a population is infected. The disease may be present in every individual; however, the symptoms of the disease do not appear equally across age groups.

(2) Hyperendemic diseases: A disease is termed hyperendemic when it is constantly present at a high rate and is equally common among all age groups.

Common Endemic Diseases

1. Malaria: Malaria is a mosquito-borne disease, and children, pregnant women and travellers are more prone to the disease. The female Anopheles mosquito transfers Plasmodium parasites from its saliva into the person's blood, which enters the bloodstream, moves up to the liver and reproduces. As malaria is transmitted by blood, it can also be transmitted through a transfusion, an organ transplant, and the use of shared syringes. Some of the signs and symptoms of malaria are kidney failure, headache, diarrhoea, fatigue, body aches, fever, nausea and vomiting, sweating, seizures, shaking chills, anaemia and bloody stools [6]. Malaria is endemic to Africa.

2. Chagas disease: Chagas disease (CD) is a life-threatening disease caused by a protozoan parasite named Trypanosoma cruzi (T.cruzi). The symptoms of CD can result from mild to moderate [7].

3. African sleeping sickness: Also termed as African trypanosomiasis, African sleeping sickness or simply sleeping sickness is an insect-borne parasitic infection of humans and other animals. It is caused by the species Trypanosoma brucei [8].

4. Hepatitis B: Hepatitis B is a DNA virus that is a member of the Hepadnaviridae family. It is often transmitted through infected bodily fluids like blood, semen and vaginal secretions [9].

5. Human Immunodeficiency Virus (HIV): HIV is a deadly virus that causes a chronic, potentially life-threatening condition called Acquired Immunodeficiency Syndrome (AIDS) [10].

Endemic, Epidemic And Pandemic

1. Endemic: As mentioned before, an endemic is any disease that is present at a constant level within a society or a country.

2. Epidemic: An epidemic is when a disease/condition spreads rapidly to a large number of people in a given population over a short time period [11]. An epidemic necessarily does not have to be a disease but can also be a health condition, such as obesity [12]. Epidemics can follow predictable patterns. Some examples of an epidemic are West Nile fever, black death, the plague of Justinian.

Here are the characteristics of an epidemic:

• An epidemic can be triggered by changes in an infectious agent, such as increased virulence, changes in host susceptibility to the infectious agent, etc.
• An epidemic disease is not required to be contagious.
• Epidemics can have a common source outbreak or a propagated outbreak.

3. Pandemic: A pandemic describes the rapid spread of a transmissible infectious/communicable disease globally [13]. An epidemic transforms into a pandemic once it becomes global and affects a large per cent of the population. Most importantly, the term pandemic is used to describe the rate and distance of the spread of the disease and not the severity of the disease. Currently, the world has two prominent pandemics, HIV/AIDS and COVID-19. Some other examples include cholera, dengue, typhus, smallpox, leprosy, malaria etc.

Here are the characteristics of a pandemic:

• It infects a large number of people and spreads quickly.
• Caused by a new virus or a new strain of a virus that has been dormant for many years.
• It affects a wider area and can cause a high number of deaths.
• Causes social disruption, unrest and economic loss.

When Does COVID-19, A Current Pandemic, Change To An Endemic?

Generally, the WHO declares a pandemic when a disease has shown rapid growth, with an increasing growth rate, showing many more cases than the previous day [14]. A primary example of this shift from a pandemic can be viewed in the case of COVID-19.

However, here we will be looking at the way the COVID-19 pandemic becoming endemic in India. According to experts at Harvard, "the expectation that COVID-19 will become endemic essentially means that the pandemic will not end with the virus disappearing" [15]. However, scientists and health experts are hopeful that enough people will gain immune protection from vaccination and natural infection. Therefore, there will be reduced transmission, hospitalisation and deaths, even though the virus will still be prevalent [16].

Swaminathan added that "this might particularly happen in places where the population is more susceptible. Those groups who were perhaps less affected by first and second waves or those areas with low levels of vaccine coverage could see peaks and troughs for the next several months."

On A Final Note…

The WHO Chief Scientist added that because of the diverse population and immunity status in various parts of India, the COVID-19 scenario would continue the same way, with varied patterns around the country.