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Three potential futures for Covid-19: recurring small outbreaks, a monster wave

Three potential futures for Covid-19: recurring small outbreaks, a monster wave, or a persistent crisis

Scenario One: Small waves as far as the eye can see

In this future, the current peak in Covid-19 cases is followed over the next two years by crest and dip, crest and dip. The crests will be less than half the size of this spring’s outbreak, with some of the highest numbers coinciding with flu season next fall and troughs this summer and next. There will likely be regional variation due to factors including random outbreaks, the bad luck of having super-spreaders, and too little testing and contact tracing to extinguish new outbreaks before they explode.

The crest-and-dip possibility reflects an emerging consensus that this coronavirus has some seasonality but will not be eliminated by hot, humid weather.

“The consensus among scientists is that climate is unlikely to substantially suppress Covid-19 on its own during the summer of 2020 because we will still have a population that is almost completely susceptible to the virus,” biologist Marta Shocket of the University of California, Los Angeles, told reporters. As a result, any seasonal reduction “won’t have as big of an effect.”

That’s because of how the virus is transmitted. Heat and humidity can kill virus on surfaces, said Adalja, “but in the summer, there will still be plenty of people who can transmit it person-to-person,” by sneezing, coughing, and even speaking.

How many people? “It is our estimate that there is maybe a 20% reduction in transmissibility in the summer,” said epidemiologist Marc Lipsitch of Harvard T.H. Chan School of Public Health, who helped develop the scenarios. “If it’s similar to the other [four] human coronaviruses,” which cause common colds, “that’s not enough to stop it, just to slow it down,” he told JAMA Live.

Osterholm’s summertime mini-wave shows more than a 20% reduction in cases, however, reflecting what experts predict will be one of the pandemic’s long-lasting legacies: Governors can open up bars and beaches all they want, but large indoor gatherings will still likely be off-limits, and many people will continue to practice voluntary social distancing.

“Even without mandates for social distancing, people will be doing it anyway,” Adalja said. “It’s been built into our lives.” As a result, he said, “spectator sports and rock concerts probably won’t be part of the equation. I suspect certain malls will close; they were already dying, so [people’s reluctance to be close to others] is likely to be their death knell.”

Measures that retailers, employers, and others are readying for when they re-open, from staggering work shifts to erecting partitions between cubicles to sending home any employee who runs even a slight fever, the new normal will lock in some of the physical distancing that has kept the worst forecasts for Covid-19’s first wave from coming true. For many, donning a face mask before meeting friends at a park or going to the gym will become as natural as pocketing their cellphone. At restaurants, patrons will likely have their temperatures taken before being seated and servers will wear a mask and gloves, Gov. Gavin Newsom of California predicted last month.

And when local outbreaks occur anyway, those measures will become stricter, even if only through voluntary measures. Many workers, frightened by a local flare-up, will telecommute if they can. People will again shun public transit, even taxis and ride apps. They will postpone scheduled surgeries and doctor visits, especially as telemedicine takes hold.

“If you can speak to a doctor on the phone instead of getting in your car, driving through traffic, and traveling to the surgery … well, who wouldn’t want that?,” said futurist Patricia Lustig, CEO of the consulting firm LASA Insight.

And then the outbreak will dissipate again, thanks to such measures. Many people will take that as a signal that it is safe to let down their guard. Social distancing will be less strict. The next wave will hit … over and over until so many people have been infected, or a vaccine succeeds, to produce herd immunity.

Said Osterholm, “I keep telling people, the outbreak will not end with this one wave.”

Hyacinth Empinado/STAT; Source: Michael Osterholm/University of Minnesota

Scenario Two: History redux

March 1918 brought the first, moderate wave of the Spanish flu. Cases fell over that summer, but six months later, in the fall, the epidemic exploded. That was followed by smaller peaks in early 1919. And then the pandemic ended. The influenza pandemics of 1957 and 1958, and 2009’s swine flu, followed a similar pattern.

In this scenario, rather than reappearing throughout the year as the crests and troughs of the first scenario, Covid-19 would return with more ferocity in the late summer and fall and then dissipate, settling into a small but near-constant number of cases. “You would have what we call a case cliff,” Osterholm said.

The precipitous, and lasting, fall-off would have two causes. First, so many people would be infected in the moderate first wave (now) and the gargantuan second wave (peaking around October) that the population might approach herd immunity. Second, the second wave, Osterholm said, “would absolutely take the health system down.”

Avoiding that was the whole point of efforts to “flatten the curve” in the U.S. beginning in March, and they largely succeeded. But even if hospitals and others use the summer lull to load up on personal protective equipment, ventilators, and other needs, and to otherwise prepare for a full-blown return of Covid-19 in the autumn and winter, it would likely not be enough.

“If we also had a bad flu season, it would be really difficult for hospitals to cope,” Hopkins’ Adalja said.

An imminent or actual crash of the health care system, similar to what northern Italy experienced in March, would force national, state, and local officials to impose mitigation measures even stricter than those of the last six weeks, which — as happened in China from late January to early March — would mostly snuff out Covid-19.

Because the new coronavirus would continue to circulate, like the four other human coronaviruses, there would still be low-level transmission. But cases would be so few they would hardly count as “outbreaks;” instead, Covid-19 would be with us at a fairly low level, perhaps thousands of cases at any one time.

Hyacinth Empinado/STAT; Source: Michael Osterholm/University of Minnesota

Scenario Three: The worst Groundhog Day

If everything breaks wrong, “we just keep having outbreaks in this city or that city and we keep trying to smother them,” Osterholm said, who calls this the “slow burn” scenario.

The waves keep coming because the size of the outbreaks that follow the current one are smaller than in the monster-wave second scenario. It therefore takes longer for population immunity to build up. Local outbreaks occur, worse in some places than others due to, among things, different capacity to conduct widespread, regular testing and contact-tracing.

No past influenza pandemic has ever followed this pattern. There are two reasons Covid-19 might, however.

One is biological: Coronaviruses, as shown by the four endemic ones, are frighteningly adept at continuing to circulate and never disappearing (the SARS coronavirus in the early 2000s was an exception).

The other is sociological: There are real questions about society’s capacity to withstand another economic shutdown, let alone repeated ones. In the future, those policies, at least in some cities and states, may well be less stringent, and therefore less effective at controlling outbreaks, than those imposed this spring. That’s why future outbreaks in this scenario keep coming, with durations and case loads comparable to the current one.

Do the endless waves mean that social distancing will have to be reimposed over and over, forcing the repeated closures of businesses that just reopened and the laying off of employees whose jobs keep being eliminated? Although it’s hard to remember, the stay-at-home orders, business shutdowns, and other mitigation measures were all in service of flattening the curve: slowing the spread of Covid-19 enough to keep the number of patients needing hospitalization, intensive care, or a ventilator no greater than the health system’s capacity. Flattening the curve did not mean zero cases and deaths, or even a few thousand.

If that remains the goal for future Covid-19 waves, then mitigation might not be as severe, as a growing number of epidemiologists recognize: Having seen how disastrously short of supplies and capacity they were, many hospitals will use the summer lull “to manage capacity better and make adjustments to be better able to absorb a surge of cases,” Adalja said. “Hopefully, it won’t be a calamity every time.”

Ironically, that may increase somewhat people’s tolerance for high numbers of illnesses, especially if the arrival of effective treatments means the return of Covid-19 is less lethal than it was initially.

Society must referee what Leung calls “a three-way tug of war” among a trio of competing needs: to keep cases and deaths low, to preserve jobs and economic activity, and to preserve people’s emotional well-being. “It’s a battle between what we need to do for public health and what we need to do for the economy and for social and emotional well-being,” he said. If the public health part of the tug-of-war weakens, then the waves will keep on coming through the end of 2022.

And which scenario is most likely? Osterholm isn’t sure. “This virus is on its own time schedule,” he said. “But we will have some tough months ahead.”

By Sharon Begley @sxbegle

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