“And then we went back to the drawing board over the last week or two and worked from the ground up, utilizing actual reporting of cases,” she explained.

Birx singled out projections by the Institute for Health Metrics and Evaluation at the University of Washington in Seattle, suggesting that model is close to how government experts see the situation.

As of Tuesday morning, the IHME forecast predicted about 84,000 U.S. deaths through early August, with the highest number of daily deaths occurring April 15. That would be three days after Easter.

The model generated attention because it offered the first state-by-state outlook for the next several months, based on how the outbreak is reacting to the various containment efforts put in place at different times around the country. It shows how the outbreak will unfold at a different pace in various states. For example, the model predicts it will peak about a month earlier in New York than in Texas.

The IHME model is what’s called a “planning model” that can help local authorities and hospitals plan for such things as how many ICU beds they’ll need from week to week.

“Nobody has a crystal ball,” said Dr. Christopher Murray of the University of Washington, who developed the model. It is updated daily as new data arrives. While it is aimed at professionals, Murray hopes the model also helps the general public understand that the social distancing that’s in place “is a long process.”

Just like a massive evacuation can save lives in a Category 4 hurricane, social distancing and shuttered workplaces can slow the rate at which the virus spreads, in hopes that severe illness and deaths may not hit a particular locality all at once. Overwhelmed hospitals unable to care for patients could make things worse.

Fauci says models are useful, but they represent well-informed guesswork. They involve a wide span of possible results, from a best-case scenario to calamitous impacts. Usually the mid-range estimate gets cited. But sometimes, it’s worst-case projection.

“What I like to do — as a scientist, a physician, a public health official — is to not ignore models,” said Fauci. But to “look at the data as it’s evolving and do everything you possibly can to mitigate that instead of getting overly anxious about the extremes of the model.”

For most people, the new coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia, or death. The vast majority of people recover.

The virus has caused a global pandemic that has sickened about 800,000 people and killed tens of thousands, according to figures compiled by Johns Hopkins University.