Detailed models suggest the coronavirus that causes COVID-19 could resurge as late as 2024.
Hopefully you're comfortable wherever you're sheltering in place, because a new study out of Harvard University's T.H. Chan School of Public Health says periods of social distancing may be necessary into 2022 to curb the spread of the coronavirus SARS-CoV-2.
Sociologists have suggested that some social distancing methods, like avoiding hugs and handshakes, could persist beyond the end of the pandemic, but the paper published Tuesday in the journal Science notes that even after the spread of the virus appears to wane, "a resurgence in contagion could be possible as late as 2024."
"The total incidence of COVID-19 illness over the next five years will depend critically upon whether or not it enters into regular circulation after the initial pandemic wave, which in turn depends primarily upon the duration of immunity that SARS-CoV-2 infection imparts," the researchers, led by Harvard research fellow Stephen Kissler, write in summary.
The peer-reviewed study focused in large part on the question of how long immunity from exposure to the new coronavirus or cross-immunity from other coronaviruses might protect against infection. (It should be noted that this is not the same as the immunity that could come from a vaccine, which is still in development.) It ran computer-modeled scenarios using data from what we know so far about SARS-CoV-2, combined with data on two related coronaviruses thought to be the second most frequent cause of the common cold (behind rhinoviruses).
If immunity to SARS-CoV-2 is similar to that of the milder coronaviruses included in the study, it may last for less than a year, leading to annual outbreaks akin to what we see with cold and flu season. In another scenario, immunity may last closer to two years, raising the possibility of biennial outbreaks with smaller flare-ups in the intervening years.
Harvard's computer models showed SARS-CoV-2 could produce a substantial outbreak at any time of year, with an outbreak that starts in the autumn or early winter being more serious than one that establishes itself in the late winter or spring. Similar pandemics have waned when temperatures rise in the summer, only to see infection rates increase again in the autumn, a pattern seen with the 1918 flu pandemic.
The models also showed that places with more defined seasons like New York could see steeper summertime reductions in infection than warmer climes like Florida, but this is followed by a steeper peak in infections when winter returns. In essence, colder places could see more drastic seasonal pendulum swings in infection.
In one scenario, immunity to the new coronavirus lasting about two years combined with cross-immunity from less serious coronaviruses could nearly eliminate SARS-CoV-2 before a resurgence in 2024.
So far the US and most other nations have responded to the pandemic with an initial round of lockdowns and social distancing that are just beginning to ease in China and parts of Europe, but the researchers warn that one round of isolation may not be enough.
"One-time social distancing efforts may push the SARS-CoV-2 epidemic peak into the (northern) autumn," they write. "Intermittent distancing may be required into 2022 unless critical care capacity is increased substantially or a treatment or vaccine becomes available."
The researchers acknowledge that their analysis comes with a number of limitations. The computer models used don't take into account a number of factors, like the impact of reopening schools, differences in geography and how the virus affects various age groups, not to mention our incomplete and evolving understanding of the virus itself.
"The authors are aware that prolonged distancing, even if intermittent, is likely to have profoundly negative economic, social and educational consequences," they write. "We do not take a position on the advisability of these scenarios given the economic burden that sustained distancing may impose, but we note the potentially catastrophic burden on the health care system that is predicted if distancing is poorly effective and/or not sustained for long enough."
To help determine the way forward, the researchers say a better understanding of immunity to the virus is key, as is epidemiological surveillance of the disease, which can be done through widespread testing and contact tracing.
As of this writing, there have been nearly 2 million confirmed cases of COVID-19 infection worldwide, and over 125,000 deaths. By most estimates, a vaccine is at least a year away.