Misplaced Analogies: COVID-19 Is More like a Wildfire Than a Wave

New coronavirus infections have soared to their optimum ranges in 5 states, as some leaders pause plans to reopen organizations additional. The history highs—in Arizona, Florida, Ga, Nevada, and South Carolina—mark a relating to increase in circumstances that is now stretching into its 3rd consecutive week. Far more than two.five million persons in the United States have been contaminated with coronavirus and at least a hundred twenty five,000 have died, increased than any other place.

Early in the pandemic, Sarah Cobey, an epidemiologist and evolutionary biologist at the University of Chicago, pivoted her personal investigate on influenza to design the dynamics of COVID-19. In this article she solutions some inquiries from Scientific American contributor Marla Broadfoot about why we are viewing an uptick in cases—and no matter whether they herald a dreaded second wave of the ailment.

[An edited transcript of the job interview follows.]

This month much more than 20 states have documented a increase in everyday coronavirus circumstances. Is this uptick section of a initial or second wave? Or are those groups even a helpful way of looking at this pandemic?
I think this is a challenging query, simply because I am not confident that it is that helpful to think about the dynamics that we are viewing as waves. We know that influenza and quite a few other respiratory pathogens cause these wavelike epidemics, wherever the crests and troughs of the waves are set by the portion of the population that is susceptible. Epidemics start out declining when the susceptible population falls underneath the threshold for herd immunity. And they can get off once more at the time the susceptible portion rises earlier mentioned it. But what we are looking at right here is a virus that obviously has not been circulating in a population for a extensive time—and to which most of us are nonetheless susceptible. There is no rationale that we should be viewing the type of wavelike epidemic dynamics that we have seen for other respiratory pathogens. Alternatively what we are viewing is a massive epidemic that could melt away through the population speedily until we do a little something to slow transmission, which is what we are currently executing with interventions these types of as social distancing and masks. It is feasible that, about time, COVID-19 could start out creating cyclical, flulike waves. But that is decades away.

If we were being to use the wave terminology that is in frequent parlance, what types of dynamics with the ailment should we assume to see up coming?
We could see all unique types of resurgences or waves. And it actually depends on what we do. We could have just a single massive wave like Japan, which seems to be taking care of the virus extremely effectively, if we adhered to similar interventions until finally a vaccine is developed. We could see a little something like a second wave if persons just gave up entirely, for instance, on social distancing or putting on masks. But I do not think that is dependable with our behavior.

Some professionals and politicians have prompt the new coronavirus could die down in the summer time. However new circumstances are nonetheless on the increase. Do these recent tendencies explain to us everything about the seasonal character of the pathogen?
Most respiratory viruses that have been studied seem to have bigger premiums of transmission in the winter and lower premiums in the summer time. And we know that this seasonality is not wholly driven by human behavior. It seems like there are these other forces that are influencing this seasonal timing, these types of as temperature, humidity and sunlight. I think it would be bizarre if the new coronavirus were being not in the same way delicate to the seasons. If you just appeared at the essential math right here, on the other hand, variations in human behavior are heading to have a considerably increased affect on transmission. As you pointed out, we are viewing transmission finding up in quite a few states. But I suspect points would be even even worse if it were being not for summer time.

What classes could be gleaned from previous flu epidemics to have an understanding of what we are viewing ideal now with the COVID-19 pandemic?
1 point we have by now talked about is seasonal consequences. For instance, the H1N1 flu pandemic of 2009 experienced a spring wave that died out about the summer time and then came again somewhat early in the slide. The summer time temperature could in the same way have an affect on the transmission of COVID-19. But what we have right here is a virus that is extremely transmissible. That tends to make it challenging to draw a immediate comparison to any other epidemic we have experienced ahead of. All earlier flu pandemics have been in populations with preexisting immunity, so even nevertheless it was a new virus, persons by now experienced a great deal of immunity developed up from exposure to earlier flu viruses.

Yet another point we are viewing is variation in the sizing and timing of COVID-19 epidemics—among not just states but countries—that can be traced to unique interventions that experienced been in area in those locations. That is a little something that we also observed with the 1918 flu pandemic. We are viewing once more that the timing of these waves is possibly less than our management. It will rely on how a great deal we are heading to pull again on our personal interventions.

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