Worst Case Estimates from the Experts
https://www.nytimes.com/2020/03/13/us/coronavirus-deaths-estimate.html
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professor at the Johns Hopkins Whiting School of Engineering who models epidemics, “those model parameters are no longer applicable,” so short-term forecasts are likely to be more accurate.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 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.
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.
In the absence of public projections from the C.D.C., outside experts have stepped in to fill the void, especially in health care. Hospital leaders have called for more guidance from the federal government as to what might lie in store in the coming weeks.
Even severe flu seasons stress the nation’s hospitals to the point of setting up tents in parking lots and keeping people for days in emergency rooms. Coronavirus is likely to cause five to 10 times that burden of disease, said Dr. James Lawler, an infectious diseases specialist and public health expert at the University of Nebraska Medical Center. Hospitals “need to start working now,” he said, “to get prepared to take care of a heck of a lot of people.”
Dr. Lawler recently presented his own “best guess” projections to American hospital and health system executives at a private webinar convened by the American Hospital Association. He estimated that some 96 million people in the U.S. would be infected. Five out of every hundred would need hospitalization, which would mean close to five million hospital admissions, nearly two million of those patients requiring intensive care and about half of those needing the support of ventilators.
Dr. Lawler’s calculations suggested 480,000 deaths, which he said was conservative. By contrast, about 20,000 to 50,000 people have died from flu-related illnesses this season, according to the C.D.C. Unlike with seasonal influenza, the entire population is thought to be susceptible to the new coronavirus.
The experts said these projections were critically important to act on, and act on quickly. If new infections can be spread out over time rather than peaking all at once, there will be less burden on hospitals and a lower ultimate death count. Slowing the spread will paradoxically make the outbreak last longer, but will cause it to be much milder, the modelers said.
“All U.S. cities and states have the natural experiment of the cities that have preceded us, namely the superb response of Singapore and Hong Kong,” said Dr. Michael Callahan, an infectious disease specialist at Harvard. Those countries implemented school closures, eliminated mass gatherings, required work from home, and rigorously decontaminated their public transportation and infrastructure. They also conducted widespread testing.
They were able to “reduce an explosive epidemic to a steady state one,” Dr. Callahan said.
