Living with endemic Covid will not be painless
The writer is a science commentator
By some accounts, the season finale of the pandemic approaches. Omicron appears to be less severe than the Delta variant. Some of this will be down to immunity built up through vaccination and infection; research also suggests the variant prospers more in the upper airways than in the lungs. Accordingly, hospital stays are shorter and fewer patients require intensive care.
That has framed the belief that Sars-Cov-2, the virus that causes Covid-19, is settling into the background alongside other relatively benign coronaviruses that mostly induce symptoms of the common cold. The sense of an imminent ending is reinforced by the image of a “mild” variant coupled with many references to “endemicity” and “learning to live with the virus”. Nadhim Zahawi, former UK vaccines minister, said recently he hoped the UK would be “one of the first major economies to demonstrate to the world how to transition from pandemic to endemic”.
Scientists suggest that such framing is misguided. While its exact meaning is debated, “endemic” refers to a disease that is constantly present in a certain area, irrespective of severity. Malaria, for example, is endemic in tropical and subtropical areas, and killed more than 600,000 people in 2020, according to the 2021 World Malaria Report. People live with it — but not painlessly.
“Endemicity does not imply mild disease, and mild disease does not imply endemicity,” says Elizabeth Halloran, who directs the Centre for Inference and Dynamics of Infectious Diseases in Seattle. “The move towards endemicity has to do with reaching a dynamic equilibrium where on average one person infects one other person. This could include seasonality or other fluctuations.”
The relatively stable presence of an endemic disease is a world away from the unpredictable spikes and surges of the current pandemic. As Harvard University epidemiologist Bill Hanage tweeted: “For the avoidance of doubt, Omicron is not endemic right now in much the same way as the moon is not a hamster.”
Though vaccines will help, Halloran says, “there is not much we humans can intentionally do to move towards endemicity . . . a lot depends on how the virus evolves”. She cannot predict its next step, other than that any new variant will need to be either more transmissible or better at escaping immunity — or both — to get the better of Omicron.
Future severity remains a big unknown. There is no law dictating that a virus must become milder over time. “It is very hard to predict the evolution of virulence,” says Eddie Holmes, the evolutionary biologist who helped scientists in China publish the Sars-Cov-2 genome sequence in January 2020. “It could go up, go down, or stay the same. It is certainly still possible for a more virulent variant to emerge in the future.” Ongoing transmission helps to generate new variants; the World Health Organization added a record 15m new cases to its dashboard last week.
Omicron has still sparked hospital surges, showing the sheer numbers of people infected can wipe out any gains from a drop in severity. One director of public health in north-west England suggested in the British Medical Journal that the Omicron surge might cause more non-Covid than Covid deaths due to pressure on the NHS, and this risk had not been clearly communicated.
Other possibilities need communicating, too. There are generally four long-term options for a circulating pathogen: extinction, as is thought to have happened to the less transmissible coronavirus that caused the 2002-3 Sars-1 epidemic, thanks to concerted public health efforts; global eradication, as with smallpox through vaccination; regional or local elimination, as China is trying to achieve with its zero-Covid policy; and endemicity, where the disease is a constant presence.
The pandemic coronavirus, contagious before symptoms appear, is so adept at finding new people to infect, including those it has infected before, that extinction and global eradication look impossible. Local elimination requires containment policies and border controls that many find too draconian.
That leaves endemicity. Prior immunity from vaccination and infection is easing the health burden but endemic does not mean benign; it does not mean the virus has given up evolving; and, as with malarial bednets, it does not mean permanently casting aside suppression measures such as vaccination, masks and ventilation.
Tempting though it is, we must beware the framing of endemicity as game over.
Letter in response to this article:
Clear-headed view of what living with Covid means / From Noah Berman, Bristol, UK