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Opinion: Endemic Does Not Mean End of Disease

Opinion: Endemic Does Not Mean End of Disease

A health worker sprays disinfectant at the Howrah bridge during COVID-19 lockdown in Howrah, Monday, May 4, 2020. Photo: PTI/File

The World Health Organisation (WHO) announced on May 5 that COVID-19 is no longer an international public health emergency. This has raised hopes that the pandemic is on its way to becoming endemic. To the public, this may equate with no further restrictions (self-imposed or otherwise) and going back to the ‘new normal’ without worry.

Unfortunately, beyond the basic epidemiological definition of an endemic disease being one with a constant, predictable, or expected presence, there isn’t much consensus on what it implies. By this broad definition, endemicity doesn’t guarantee to be milder or rarer than what it was when the pandemic was in full rage. Infection rates can remain high, causing worry for the susceptible (aged, unvaccinated, immune-compromised or deficient individuals), but they only need to remain static (i.e., no sudden surges).

The more pragmatic and optimistic view of SARS-CoV-2, the virus that causes COVID-19, becoming endemic is that a significant proportion of the population will have achieved immunity through vaccination and/or natural infection resulting in reduced transmission and hopefully, lesser morbidity and mortality.

However, we must not forget that endemic diseases continue to infect millions of people around the world each year. Collectively, some endemic diseases such as malaria, Hepatitis B, dengue, tuberculosis, HIV, and influenza still kill hundreds of thousands despite vaccines and treatments being available. It is still a mystery what endemic COVID-19 will look like and the rush to rejigger COVID-19 as endemic (and hence reframing as something acceptable) may be missing a few points such as the fact that while a pandemic strain of the virus may become endemic, an endemic strain of the virus can very quickly become an epidemic and pandemic again!

Medics in protective suits are seen in a containment zone during the COVID-19 pandemic, in Aligarh, May 2, 2020. Photo: PTI

This is especially true when multiple strains of an endemic virus continue to circulate in the population and can potentially mutate or recombine to come up with a version the world has not seen before (the 1968 flu pandemic caused by a novel H3N2 flu virus). The vaccines for COVID-19 protect us from severe health complications (death and serious hospitalization) but they do not stop transmission between an infected (symptomatic or asymptomatic) individual and an uninfected person. Hence the virus will continue to circulate amongst us and continued surveillance by monitoring agencies will be key in preventing an outbreak.

We must also consider that endemicity does not guarantee equal disease burden for all as it implies. During the pandemic, underprivileged communities across the world had disparate access to medical care (including COVID-19 vaccines and boosters) and sanitation, two critical determinants for ensuring a reduced burden of COVID-19. The endemic status of the virus unfortunately does not change that trajectory of disparity. What’s endemic here is not necessarily endemic there!

Endemicity demands being in control of a disease that we must live with and manage. For Malaria, we continue our efforts to eradicate mosquitoes; for flu, we continue to vaccinate the susceptible population every year and promote handwashing; for HIV, we continue to rely on promoting safe-sex behaviour. Why will it be any different for COVID-19? It is in the nature of the virus to mutate, and Omicron-like events can happen every year without a hint. We must therefore continue to vaccinate, update our vaccines (just like the flu), and practice hand hygiene and respiratory hygiene behaviours diligently to keep COVID-19 endemic. 

Watch: COVID-19 Has Become Endemic, Says Virologist Gagandeep Kang

What does endemicity for COVID-19 mean?

Our epidemiological history has taught us that respiratory viruses (the ones which spread through coughing, sneezing, and talking) emerging from reservoirs in the wild, jumping over the species barrier to infect humans, and then sweeping the globe before settling into an endemic behaviour can cause outbreaks that can result in significant mortality and morbidity. Examples include the 1957 flu pandemic caused by an A/H2N2 influenza virus, the 1968 flu pandemic from an A/H3N2 influenza virus, and the 2009 “swine flu” pandemic, from an A/H1N1 influenza virus.

In all the above cases, our pre-existing immunity did not guarantee any protection. Flu viruses are notorious for evading the immune system by changing their antigenic signatures to fool the existing antibodies. It remains to be seen what evolutionary roadmap the circulating variants of SARS-CoV-2 will choose. Studies are ongoing to understand what the correlates of vaccine-induced protection from COVID-19 are. We still don’t know how long or how potent will be our vaccine-conferred protection against next year’s circulating ‘endemic’ strain of SARS-CoV-2.

While the virus is (hopefully) going to settle for an ‘endemic’ status quo, the difficult question for policymakers and healthcare professionals is how much burden of COVID-19 are we willing to tolerate in the population? According to reports from CDC, between 20,000 to 60,000 people die every year in the US from endemic flu. Are we OK if this mortality rate translates for endemic COVID-19 as well? Should we instead remind ourselves of the best practices (frequent handwashing, masking in crowded places) that became second nature during the pandemic and don’t leave anything for providence and the will of the ‘endemic’ virus? If we forget our lessons from the recent past, borrowing from Shakespeare, “ the fault…is not in our stars, but in ourselves”.

Sayandip Mukherjee has a PhD in molecular virology from Rutgers University, New Brunswick, NJ, US. He presently works as a senior research scientist in the R&D wing of a multinational company based out of Bangalore. The views expressed in this article are his own.

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