The Greek historian Herodotus lived through the plague of Athens, one of the world’s first great pandemics. He wrote, “Circumstances rule men; men do not rule circumstances.”
So it is with COVID-19. In the U.S., we are currently in the middle of an autumn downturn in COVID-19 cases, and no one can say whether this will be the end. It is clear, however, that the U.S. is repeating a mystifying cycle of case rise and fall that has been seen in other countries. For reasons unknown, cases surge for six to 10 weeks and then fall predictably in a similar fashion for at least an equal period.
At present, we are nearing the eighth week of the downturn in cases.
With luck, if the trends hold, cases are likely to fall for at least another one to three weeks. After that, no one can say what will happen. A new variant, delta-plus, has emerged sporadically, which might complicate any late-year predictions.
Why does COVID-19 behave like this? In an admission of humility somewhat surprising for COVID-19 experts, prominent U.S. public health researcher Michael Osterholm conceded, “We still are really in the cave ages in terms of understanding how viruses emerge, how they spread, how they start and stop, why they do what they do.”
Because rises in cases are easier to explain, they often draw more attention than case declines. The six- to 10-week interval may be the time it takes for spread to susceptible hosts. Especially with contagious variants, dramatic surges may be fueled by 20% of infected patients – the so-called superspreaders, Nature.com suggests. Subsequent infections in the 80% of the population who are less apt to spread infection are likely to trigger greater precautions (masking, lockdowns, distancing). That, along with fewer susceptible hosts, may stop the spread – until a new cycle begins.
Greater attention to case declines might yield more answers. Dramatic case declines as occurred in Japan (97% in nine weeks) and Indonesia (95% in 10 weeks) have left the experts flummoxed. Vaccination, masking and social distancing all played a factor in the downturns, but are almost certainly not the primary reason.
Japan was relatively late to vaccination and never instituted a full lockdown. Earlier this year, India went from a peak of 400,000 daily cases to 40,000 daily cases in eight weeks, despite having a low vaccination rate and minimal social distancing.
Why would social behavior, so variable in different countries, result in such similar cycles of infection? We are left with two other factors, both of which we know very little about – the virus itself and host immunity. Does the virus have a built-in regulator that governs its behavior and limits it to finite cycles of infection before it retools? Can the virus, like Dracula, shut itself off at two-month intervals and reemerge in slightly different forms?
Are there different patterns of host immunity, natural and acquired, in different countries? Does immunity explain the lower rate of infection and mortality in East Asia and Africa compared to Europe and the Western Hemisphere?
The medical textbooks of the next hundred years will note that the COVID-19 pandemic is the first time scientists finally have the technical resources and opportunity to investigate the crucial issue of pandemic immunity.
We do have some say in our collective fate. Get vaccinated, practice social distancing and mask when appropriate. In addition, ensure buildings are well-ventilated and practice good hygiene. We may not rule our circumstances, but we can help one another.
Dr. Cory Franklin is a retired intensive care physician. Dr. Robert Weinstein is an infectious disease specialist at Rush University Medical Center.
The Chicago Tribune