Officials at the C.D.C. and epidemic experts conferred last month about what could happen in the U.S.
The C.D.C. scenarios have not been publicly disclosed. Without an understanding of how experts view the threat, it remains unclear how far Americans will go in adopting socially disruptive steps that could help avert deaths.
Officials at the U.S. Centers for Disease Control and Prevention and epidemic experts from universities around the world conferred last month about what might happen if the new coronavirus gained a foothold in the United States. How many people might die? How many would be infected and need hospitalization?
One of the agency’s top disease modelers, Matthew Biggerstaff, presented the group on the phone call with four possible scenarios — A, B, C and D — based on characteristics of the virus, including estimates of how transmissible it is and the severity of the illness it can cause. The assumptions, reviewed by The New York Times, were shared with about 50 expert teams to model how the virus could tear through the population — and what might stop it.
The C.D.C.’s scenarios were depicted in terms of percentages of the population. Translated into absolute numbers by independent experts using simple models of how viruses spread, the worst-case figures would be staggering if no actions were taken to slow transmission.
Between 160 million and 214 million people in the U.S. could be infected over the course of the epidemic, according to one projection. That could last months or even over a year, with infections concentrated in shorter periods, staggered across time in different communities, experts said. As many as 200,000 to 1.7 million people could die.
And, the calculations based on the C.D.C.’s scenarios suggested, 2.4 million to 21 million people in the U.S. could require hospitalization, potentially crushing the nation’s medical system, which has only about 925,000 staffed hospital beds. Fewer than a tenth of those are for people who are critically ill.
The assumptions fueling those scenarios are mitigated by the fact that cities, states, businesses and individuals are beginning to take steps to slow transmission, even if some are acting less aggressively than others. The C.D.C.-led effort is developing more sophisticated models showing how interventions might decrease the worst-case numbers, though their projections have not been made public.
“When people change their behavior,” said Lauren Gardner, an associate professor at the Johns Hopkins Whiting School of Engineering who models epidemics, “those model parameters are no longer applicable,” so short-term forecasts are likely to be more accurate. “There is a lot of room for improvement if we act appropriately.”
Those actions include testing for the virus, tracing contacts, and reducing human interactions by stopping mass gatherings, working from home and curbing travel. In just the last two days, multiple schools and colleges closed, sports events were halted or delayed, Broadway theaters went dark, companies barred employees from going to the office and more people said they were following hygiene recommendations.
The Times obtained screenshots of the C.D.C. presentation, which has not been released publicly, from someone not involved in the meetings. The Times then verified the data with several scientists who did participate. The scenarios were marked valid until Feb. 28, but remain “roughly the same,” according to Ira Longini, co-director of the Center for Statistics and Quantitative Infectious Diseases at the University of Florida. He has joined in meetings of the group.
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The C.D.C. declined interview requests about the modeling effort and referred a request for comment to the White House Coronavirus Task Force. Devin O’Malley, a spokesman for the task force, said that senior health officials had not presented the findings to the group.
The assumptions in the C.D.C.’s four scenarios, and the new numerical projections, fall in the range of others developed by independent experts.
Dr. Longini said the scenarios he helped the C.D.C. refine had not been publicly disclosed because there remained uncertainty about certain key aspects, including how much transmission could occur from people who showed no symptoms or had only mild ones.
“We’re being very, very careful to make sure we have scientifically valid modeling that’s drawing properly on the epidemic and what’s known about the virus,” he said, warning that simple calculations could be misleading or even dangerous. “You can’t win. If you overdo it, you panic everybody. If you underdo it, they get complacent. You have to be careful.”
But without an understanding of how the nation’s top experts believe the virus could ravage the country, and what measures could slow it, it remains unclear how far Americans will go in adopting — or accepting — socially disruptive steps that could also avert deaths. And how quickly they will act.
Studies of previous epidemics have shown that the longer officials waited to encourage people to distance and protect themselves, the less useful those measures were in saving lives and preventing infections.
What’s at stake in this coronavirus pandemic? How many Americans can become infected? How many might die? The answers depend on the actions we take — and, crucially, on when we take them. Working with infectious disease epidemiologists, we developed this interactive tool that lets you see what may lie ahead in the United States and how much of a difference it could make if officials act quickly. (The figures are for America, but the lessons are broadly applicable to any country.)