A popular theory that I often hear from friends is that the Coronavirus pandemic will disappear after Election Day. Not so, says the Institute for Health Metrics and Evaluation at the University of Washington, which has been the premier forecaster for the pandemic in the US. A new model by the IHME shows that, rather than spontaneously disappearing, “The worst is yet to come.”
The Coronavirus caseload in the US seems to have plateaued once again, even though death rates remain high with a seven-day average of almost 1,000 deaths per day. As in the spring, the tendency for many is to assume that the worst is over and return to normal, but a number of factors are likely to result in a resurgence of the disease this fall and winter.
“The worst is yet to come. I don’t think perhaps that’s a surprise, although I think there’s a natural tendency as we’re a little bit in the Northern hemisphere summer, to think maybe the epidemic is going away,” Dr. Christopher Murray, director of IHME, said in a conference call reported by CNBC on Friday.
He added that there are “bleak times ahead in the Northern Hemisphere winter, and unfortunately we are not collectively doing everything we can to learn from the last five months.”
Disease prediction models draw a lot of criticism and scorn at the beginning of the pandemic last spring, but as scientists have learned more about COVID-19 the models have become more accurate. Back in May, I described a “model of models” which forecasted 110,000 virus deaths by June 6. This undercounted the actual number since the total on June 6 was 114,625 deaths. Likewise, in June the IHME predicted that there would be 200,000 Coronavirus deaths by October. With almost 1,000 deaths per day and three weeks to go, it looks as though that forecast will have been on the low side as well since the US has already recorded 193,302 deaths as of Labor Day.
The IHME released three different projections that show possible outcomes under different scenarios. The best-case scenario, which assumes universal masking and strict observation of social distancing, estimates that 288,380 Americans will die of COVID-19 by the end of the year. The worst-case scenario, based on the removal of social distancing restrictions and mask mandates, is a death toll of 620,028. The most likely scenario is in the middle with a death toll of 410,450.
The new forecast estimates an increase in the daily death rate “because of seasonality and declining vigilance of the public, to reach nearly 3,000 a day in December.” Currently, there are about 850 deaths per day in the US. The US previously approached 3,000 daily deaths in the dark days of April.
“We are facing the prospect of a deadly December, especially in Europe, Central Asia, and the United States,” Dr. Murray said. “But the science is clear and the evidence irrefutable: mask-wearing, social distancing, and limits to social gatherings are vital to helping prevent transmission of the virus.”
The global death toll, which currently stands at 881,000 people, is estimated to be 2.8 million by January 1. The best and worst-case scenarios range between two and four million.
The IHME model is based upon several assumptions. Among these are that people will become more willing to interact as new cases decline and that cooler weather will encourage people to stay indoors where the virus can spread more easily. Further, the cool, dry air of fall will allow the virus to live longer.
Even though COVID-19 transmission in the US has fallen since June, there are still about 40,000 new cases every day. This elevated but stable level could provide a springboard for yet another wave of infections if people let down their guard and forego mitigation strategies, just as the relaxation of social distancing in June led to a surge of cases in July.
“One of the challenges is as soon as things look good in the community, it’s tempting to say the virus is gone,” said Lauren Ancel Meyers, professor of integrative biology at the University of Texas at Austin, in the Washington Post. “What we really should be thinking is: How did we get to this better place? By being cautious and vigilant. And instead of relaxing, we should focus on the things that worked.”
The IHME model is one of the few long long-range forecasting tools. Many models only predict four to six weeks into the future. Some critics say that the number of variables considered over a long period of time makes long-term forecasting unreliable.
“Beyond [a few weeks], it’s all conjecture and guesswork because there are so many factors we just can’t predict and factors about transmission that truthfully scientists don’t understand very well yet,” Jeffrey Shaman, an infectious-disease expert and head of the modeling team at Columbia University, told the Post. “What happens in the next few months really depends on what we do as a society the next few weeks.”
One of the biggest variables is the impact of social distancing. In the Southern Hemisphere, where winter began in June, the annual influx of flu patients has not come this year for many countries per the Wall Street Journal. In many parts of the world, strict lockdowns not only seem to be preventing a surge of COVID-19 cases but also annual flu epidemics. With much of the US open, the winter in America might well bring a different result.
The most recent CDC forecast, which uses an “ensemble” of models, predicts that national death rates will decrease slightly but agrees with the IHME estimate of 200,000 to 211,000 US deaths by September 26. The CDC model, updated on September 3, does not look beyond four weeks into the future.
The IHME’s Dr. Murray defended the long-range forecast, saying that the best and worst case scenarios were tools intended to assist policymakers and help governments to avoid the worst-case scenario. He added that a second wave is likely to happen regardless of the exact timing and that decisions made now would affect the death toll in coming months.
Most experts seem to agree on that point.
As we’ve pointed out before, models are not ironclad predictions for the future. Instead, they are estimates based on assumptions about what will happen and how people will behave. As such, they are a cautionary tale for the future but changing behavior can change the outcome.
I would bookmark the IHME projection to refer back to around New Year’s Day in order to validate whether the forecast was accurate or not. In the meantime, the core lesson is that the crisis is not over. It is important that pandemic-weary Americans maintain mitigation strategies for at least another few months until a vaccine is ready. The difference between social distancing and wearing a mask and flouting these guidelines is likely to be tens of thousands of American lives.
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