Updated: August 29, 2021 10:07:52 pm
World Health Organization Chief Scientist Dr Soumya Swaminathan recently said that Covid-19 may be entering a stage where it will become endemic, which means that some people will get infected but the levels at which it will circulate will be low to moderate.
Swaminathan said this during an interview she gave to news website The Wire, in which she said that it was “very very feasible” that the situation may continue like what it is now, with ups and downs in disease levels in different parts of the country, depending upon the natural immunity and vaccine coverage in particular areas.
When does a disease become endemic?
According to the US Centers of Disease Control and Prevention (CDC), endemic refers to the “constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area”.
According to an article published in the journal Science in 2020, when epidemics become endemic, they become “increasingly tolerated” and the responsibility of protecting against it shifts from the government to the individual.
An epidemic, on the other hand, refers to a scenario when the number of cases of the disease increases, often suddenly, which means the cases are more than the expected levels. For some rare diseases such as polio, plague and rabies even a single case can warrant investigation from health authorities.
Notably, the number of cases of a disease that are considered “constant” would be different for different areas and would also depend on the particular geographical area’s population. For instance, if 200 cases per day are considered endemic in country A that has a population of say, 200 million, the same will not be considered endemic for country B, that has a much smaller population at, say, 20 million.
What does this mean for India and the world?
Out of the seven coronaviruses known to infect humans, the ones that have emerged since the last two decades including SARS (fatality rate of 10 per cent), MERS (fatality rate between 35-36 per cent) and now SARS-CoV-2 are the ones that are a cause for worry since they are capable of causing severe illnesses and even deaths.
Out of these three, while humans are still dealing with SARS-CoV-2 and are likely to continue doing so in the coming few years, SARS (emerged in China) and MERS (emerged in Saudi Arabia) were locally contained. The last case of SARS was detected in 2003, however, MERS is still circulating.
A modelling study published by Science magazine earlier this year said that in a few years, SARS-CoV-2 may be no more virulent than the common cold, much like other benign human coronaviruses that are currently circulating in the population and do not cause severe illness.
It is not in the interest of a pathogen such as SARS-CoV-2 to become so severe that it kills all its hosts. In other words, the virus needs a host to survive, in the present case, it requires a human host to sustain its own survival, therefore as more people get infected or get vaccinated, the virus should become less life threatening, but it will still keep infecting people.
What are some factors endemicity may depend on?
It is difficult to predict when exactly will Covid-19 become endemic in India or the world. With the vaccination rollout underway and more people getting infected each day, some proportion of the people have either developed natural immunity, they either have vaccine-induced immunity or a combination of both.
As per WHO’s Covid-19 dashboard, as of August 25, there were 213,050,725 confirmed cases of the disease the world over since the start of the outbreak in 2020. The world over, some 5 billion doses of vaccines have been administered, but this is far less than what is required to fully vaccinate the global population of more than 7 billion people.
Further, most of the 5 billion doses have been administered in richer countries, which means low-income countries are far behind, partly because they are dependent on receiving vaccine imports, from programmes such as COVAX.
As per Our World in Data, as of August 26, 33 per cent of the world population has received at least one dose of a Covid-19 vaccine, and 25 per cent is fully vaccinated. 5.08 billion doses have been administered globally, and 33.85 million are now administered each day. Only 1.4 per cent of people in low-income countries have received at least one dose.
But there are supply-side constraints, which means vaccine supplies are definitely not adequate for the world’s population and even if they were, some people are hesitant to get vaccinated.
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