Has the Pandemic Peaked?

Photo: Liu Guanguan/China News Service via Getty Images

Has the pandemic peaked? COVID-19 has a way of humbling any prediction, whether clinical or epidemiological, sanguine or alarmist. And, nationally, this remains a “patchwork pandemic,” in the memorable language of the Atlantic’s Ed Yong, with different regions experiencing wildly different levels of outbreak, the scariest trajectories now mostly in rural and red states. Globally, the term “patchwork” is even more appropriate, with Brazil poised to displace the United States as the worldwide hot spot — perhaps a harbinger of trends in the southern hemisphere, though New Zealand recently discharged its last patient from the hospital. All of this makes it hard to generalize globally about the state of the disease. And it will probably be weeks before we know for sure whether the recent American plateau is just a brief pause or the start of a new normal, which signals the worst is behind us. But looking at the broad cohort of nations that have been hit hardest so far, and perhaps especially at the United States, it appears, at the moment, as though the answer may be that it is — the worst of the first wave, at least. Why would this be? One explanation, believe it or not, may be the one Donald Trump predicted, to much mockery, in the winter: warm weather.

As recently as three weeks ago, a leaked CDC model seemed to project a median outcome of 3,000 American deaths a day by June 1. Tuesday, the national figure was 629, down from 1,430 a week before. That low number reflected slow reporting over the holiday weekend, but Wednesday’s higher figure of 1,259 was still lower than the previous Wednesday’s mark — even though it was probably artificially high, reflecting some of the weekend’s toll. More significantly, Wednesday represented the first time the seven-day average had fallen below 1,000 since April 2. And while reopenings have produced noticeable upticks in caseloads and hospitalizations in a number of American states, those upticks have not been the exponential kind seen earlier in the winter. We may well see more dramatic growth in the weeks ahead, as people relax into more “normal” routines. But it seems just as likely that that we will be navigating our way through a more stable new normal, with some growth and some declines more closely approximating a long, high plateau than a real growth curve in the months ahead.

That is the picture here in the U.S., where, more than six months since the disease announced itself and four months since it arrived on American shores, there is still no federal plan to deal with it, and practically speaking, no interest in creating one. In Europe, even sputtering and haphazard national policy has made the picture look considerably better. In Switzerland, lockdown ended on May 11, and reopening has produced only a continued decline in caseloads. In the U.K., the disease appears to be in such rapid decline that vaccine researchers now worry they may not even be able to test their drug during the summer. If 10,000 volunteers were recruited for a trial, one of the researchers said this week, perhaps only 50 would even be exposed to the disease, yielding a statistically insignificant result and suggesting, over the course of a full season, that the national rate of exposure would grow by only half of one percent. That is one estimate, from one researcher trying to dampen expectations for a quick result. But in its broad strokes, it was echoed here in the United States by former FDA chief Scott Gottlieb, probably the Republican Party’s most trustworthy, straight-shooting pandemic authority. It is, frankly, a tiny estimate for potential exposure, given all of our recent anxieties about exponential growth.

So what accounts for the relative decline of the virus? Herd immunity is still far off: Serological studies, which test for the antibodies that are the surest sign an individual has been exposed to the disease, suggest that even in the hardest-hit places like New York, no more than a quarter of the population has been exposed. In most of the country (indeed, most of the world) the figure is considerably smaller — almost everywhere lower than 10 percent. Herd immunity, it is believed, arrives only when exposure reaches 60 percent, and perhaps higher. Which means that most of the population remains vulnerable. In simple models, this would suggest we could still be in a period of at least dramatic, and potentially exponential growth; more sophisticated models, which account for changes in population behavior, would predict that even the limited reopening we’ve seen over the last weeks would produce a meaningful growth of cases, hospitalizations, and deaths. Quite possibly, depending on the model, a terrifying growth. And while it is likely the case that more and more social interaction will produce some resurgence, with some areas and regions perhaps even generating case spikes, the feared, lethal “returns” from reopening simply haven’t been that notable to date.

Which brings us to weather. The possible seasonality of COVID-19 has been long theorizedand yet somewhat strikingly underemphasized in public-health messaging and the journalism that comes out of it. But a New York Times op-ed from last week walks through some of the existing research. In New York, weather alone could reduce infections by a quarter. In Phoenix, the number could be as high as 40 percent. And in places as hot as India and Pakistan, summer weather could reduce infections by more than half.

These numbers may not seem all that significant, since even in the most extreme case, summer doesn’t bring the disease anywhere close to zero. But keep in mind that, for epidemiologists, the most significant single figure in projecting the spread of the disease is what is called the “R” figure — the average number of additional infections produced by each sick person. If the number is above one, it means the disease is growing — every sick person infecting more than one more person. If it’s below one, it means it’s shrinking. Thanks to a combination of economic lockdowns, social-distancing guidelines, better hygienic practices, possible weather effects, and perhaps some additional, mysterious factors, the R figure has dropped, nationally, to just about one — with certain hot spots just above, and many states just below. Nationally, the figure has grown from an estimated low of .91 on April 27, before reopening, to an estimated 1.02 today. In this context, with the problematic hot spots just straddling the division between growing and shrinking, a weather effect between 25 percent and 40 percent is, all else being equal, enormously significant — tipping any community where infections were growing into the group of places where the disease is shrinking.

Of course, all else won’t be equal: The country is not remaining in lockdown, as state and local governments are relaxing restrictions. And in at least nine states, R has recently grown just north of one — with further worrisome growth possible as the reopenings continue. Nevertheless, it’s worth keeping in mind that our best real-time (or quasi-real-time) data about aggressive social distancing shows that people pulled back to protect themselves before lockdown orders came from political leaders, and that, despite all the fanfare about reopening, measurable economic activity like restaurant visits remain dramatically down in those states earliest to reopen, suggesting that our social-distancing practices are perhaps much more robust and enduring than expected — by both those pushing for lockdowns to end or those who want them to continue. And the more we learn from the natural global experiment in social distancing, the more it appears as though the severity of lockdowns matters less than the speed with which measures of any kind were implemented. Implemented early enough, even moderate, commonsensical measures appear to help significantly, perhaps even sufficiently. This is one explanation for why Japan has fared so well, having avoided anything like the outbreaks seen in Europe and the U.S., despite doing almost no testing and nothing like a real lockdown. It also suggests that it may both be optimal policy and socially more sustainable to gravitate toward a less restrictive baseline than stay at home: something like widespread mask-wearing and hand-washing, a ban on large-scale events, and a suggestion to avoid as much possible indoor interactions with others when you can, as long as we can — until the arrival of a vaccine, effective therapeutics, or a test-and-trace program large and capable enough to promise the quick stamping-out of any new flare-ups. Going forward, such pandemic detective work could be helped, perhaps quite significantly, by the recent discovery that sewage can predict local outbreaks of COVID-19 well before patients start complaining of symptoms and showing positive tests.

Discoveries like these are signs, if we needed more of them, that our understanding of COVID-19 remains rudimentary, and that new revisions to conventional wisdom will be arriving regularly — along with more speculative theories to test with real study. Two of those new theories have begun circulating in recent weeks, somewhat on the fringe of conventional wisdom, and while neither seems as likely to be playing a determinative role in the pandemic’s recent slowdown as weather or social distancing, both probably bear mentioning — and scrutinizing. The first is that some aspects of the “super-spreader” dynamics of the disease, by which 20 percent or fewer of patients produce 80 percent of new cases, could produce a natural flattening of the curve. But this 20/80 rule is not novel to this novel coronavirus, indeed it reflects the way that most viruses replicate and spread. Generally speaking, super-spreading experts believe that while this heterogeneity of spread might help explain some of divergent coronavirus trajectories (i.e., why one viral line died out while another replicated exponentially, or why one region was hit much harder than others), it probably does not suggest anything about the future course of the disease (because there’s no reason to think that super-spreaders are concentrated more heavily among those who’ve gotten the disease first, though social-distancing policies can reduce how many others each carrier might infect when sick).

The second intriguing theory suggests that, perhaps, many people who don’t have COVID-19 antibodies may nevertheless be immune or at least resistant, thanks to their previous exposure to other coronaviruses. This is known as “cross-immunization” or “cross-reactivity” — and one recent paper suggests that between 40 and 60 percent of unexposed patients exhibit some signs of resistance to COVID-19, theoretically picked up from other antigens. That could prove quite a significant finding, if the percentages hold up and the disease resistance is meaningful. Presumably our understanding of each of these questions will become clearer in the next weeks and months, during which time the disease seems likely to remain quite stable — continuing to infect, sicken, and in some cases kill, but at levels comparable to those the country and its peers in Europe have already experienced, not dramatically higher ones. In other words, we may be in the range of where we are today, straddling or just below an R of one, for quite a while.

This means, among other things, that warm weather may have helped buy the country another opportunity to put forth an actual pandemic response — much like the initial one bought by Chinese lockdowns and extending from the first alarms in January through the real outbreak of epidemic in the U.S. in March, which was entirely wasted by the federal government. There is no excuse for the moral and political failure of those initial months, but continued disinterest by the White House, given the 100,000 already dead, would be even more unconscionable. Indeed, health leaders are now trying to rally a long-term focus on planning coronavirus response, saying that the disease may well be with us forever — growing even more intense again, presumably, in the fall.

Of course, today’s disease level, though seemingly stable, is not exactly worth celebrating — or, rather, it would not have been worth celebrating from the perspective of December or January, when the pandemic first appeared on the horizon. Because while stabilizing the spread of the virus at any level is an achievement, and certainly better than letting it continue to grow (as it appears to be in Brazil and to some degree Sweden), not all stabilizations are equal. As Nate Silver has pointed out, stabilizing it at levels as low as, say, South Korea has (when 40 new cases in a day, nationally, is a news event) is a much more laudable achievement than stabilizing it at ours (when, given the recent history, getting under 1,000 deaths a day can play like success story).

Already, the death toll here seems astronomical — the Times won widespread praise this weekend for simply naming one percent of those who’ve died on their front page. Indeed, simply naming 1,000 victims actually ran over the front page and onto two others, and that number of names — 1,000 — was about as many as have died on average every single day during the entire 90-day pandemic. To commemorate that horrific landmark, Susan Glasser of The New Yorker rolled out a series of historical comparisons, beginning with 22 Iraq wars. She was counting only the American dead in that war, and as her colleague Ben Taub noted, and 100,000 deaths makes the toll higher than all of the American wars fought since 1945, combined.

Even at a greatly reduced infection rate, that toll is likely to grow considerably larger — about doubling, the most accurate model to date suggests, to about 200,000 by the end of August. Those historical comparisons may feel tiresome, and imprecise, since there are obvious moral differences, not to mention policy ones, between wars of choice and pandemics — not to mention things like automobile deaths, non-pandemic disease, poverty, or hunger. But the comparisons are also illuminating, since they force us to contemplate, even as things “stabilize,” the actual scale of this horror — and to consider each life lost as an inviolable unit of tragedy. And if you can find ways to minimize 100,000 — for instance, by pointing out that it was the death toll of the mostly forgotten “Hong Kong” flu of 1968 — it becomes a lot harder at twice the number. Two hundred thousand means more Americans will have died from COVID-19 than German Jews died in the Holocaust. Then comes the fall.

Has the Pandemic Peaked?