Anthony S. Fauci saw this moment coming.

Speaking to CBS’s Margaret Brennan on March 15, Fauci, a leading member of the White House’s coronavirus task force, pointed out that the measures being implemented to limit the spread of the novel coronavirus in the United States would, if effective, seem as though they were more than what was necessary. Ideally, people would not get sick — and therefore might not think they needed to maintain distance from other people at all.

“I want people to assume that I’m over- or that we are overreacting,” Fauci said, “because if it looks like you’re overreacting, you’re probably doing the right thing.”

With the number of infections appearing to level off in New York, the state at the U.S. epicenter of the pandemic, there has been an increasing focus on precisely that question: Did we go too far? On Wednesday, those posing the query got new ammunition when a leading model of the possible effects of the pandemic scaled back its estimate of the number of deaths that might be caused by covid-19, the disease caused by the virus. Last week, the model from the University of Washington’s Institute for Health Metrics and Evaluation predicted more than 90,000 deaths by August. The new estimate has the figure closer to 60,000.

Brian Kilmeade, a host on Fox News’s morning show “Fox & Friends,” used that revision to argue that the distancing measures currently in effect are unnecessary. He compared the new data from the IHME to the upper level of predicted deaths offered by the White House last week.

“The fact is when somebody says, ’200,000 people die — oops, I mean 60,000. And it’s not going to be right away, it’s going to be in August.' That’s how good we are doing — and how off the models were,” Kilmeade said. “You have to wonder, as much as social distancing’s working, I wonder if the economists are going to get in that room and say, we have to stand up this economy in some way before we are not going to be able to stand when this is all said and done.”

Rush University Medical Center was built to withstand natural disasters and biohazard incidents. It's putting that preparation to use treating covid-19. (The Washington Post)

“Right, but Brian, it’s still 60,000 people, which is a staggering number,” co-host Steve Doocy interjected.

“It’s a high number, but how many people are going to die as the country goes flat on its back for three months?” Kilmeade replied. “We’re not going to look like the same country. So the economists have to have a say in this.”

The White House apparently agrees. The Washington Post reported Wednesday that the administration would form a second coronavirus task force focused on the economy.

Kilmeade’s point is not an uncommon one, and one that can be distilled into two questions. The first is why the model was off the mark. The second is whether the distancing measures are still needed.

Why the model was revised

It’s worth noting at the outset that Fauci had repeatedly urged caution about the models.

“Models are as good as the assumptions you put into them,” he said last week, “and as we get more data, then you put it in and that might change.”

That’s what happened with the IHME model. While it always incorporated estimates of the effects of social distancing measures, the original estimates indicated by the black line above used the only available data on those distancing efforts, the response from distancing as seen in Wuhan — the Chinese city where the virus was first reported and where distancing was first put into effect.

Earlier this week, the model was revised to include new distancing data from a number of other cities in Spain and Italy after those locations reached benchmarks the modelers were tracking. It further refined its measures of social distancing to approximate the different effects of different types of distancing. That pushed the estimated toll down significantly.

The most recent adjustment made further shifts in what was predicted to happen, again based on new data. CNN's Arman Azad reported on the new changes on Wednesday.

The researchers “fine-tuned their analysis of social distancing measures after noticing that certain measures — such as school closures — appeared more impactful in some places than others,” Azad wrote. While the model always included consideration of social distancing, that consideration depended on a limited set of data that, over time, expanded outward. More information refined the model — as Fauci suggested.

As new information is gathered, estimates change. Think about life expectancies. In 2016, the life expectancy at birth was 78.6 years. But if you lived to be 75, your life expectancy extended to 87.2 years — because you had already outlived a number of other people. With new information about the person under consideration, the estimate changes.

Notice, too, that the new estimate of the number of virus deaths falls within the uncertainty window expressed in the early April estimate. The lower bound of possible deaths offered then was about 40,000 deaths — meaning that the current estimate is still within the original range of the estimate.

Why social distancing measures are still needed

One aspect of the IHME model that Kilmeade appears not to have considered is that it assumes the maintenance of social distancing measures through May.

Speaking to Savannah Guthrie on NBC on Thursday morning, Fauci made that point.

“Do you think the number of fatalities in this country will be significantly lower than the 100,000 to 240,000 first projected?” Guthrie asked.

“I do. And I believe that the mitigation — I think the American public have done a really terrific job of just buckling down and doing those physical separation and adhering to those guidelines,” Fauci replied. “As I’ve told you on the show, models are really only as good as the assumptions that you put into the model. But when you start to see real data, you can modify that model and the real data are telling us that it is highly likely that we’re having a definite positive effect by this mitigation thing that we’re doing, this physical separation.”

The idea that the embrace of distancing measures by the country has been better than expected is not a new one. President Trump made that point in a briefing on April 6.

“I really believe that the American people are doing a better job than anybody would have thought even possible, and that’s one of the reasons we can even be talking about the kind of number that we hopefully will be talking about, which is at the minimum level instead of the maximum or beyond,” Trump said. “It’s not even the maximum — it’s much beyond a maximum level, which would be horrific.”

At the briefing on Wednesday, Deborah Birx, another member of the White House task force, attributed the decline in the model’s estimates to the success of that distancing effort.

“I know many of you are watching the Act Now model and the IHME model from — and they have consistently decreased the number, the mortality, from over almost 90,000 or 86,000, down to 81,000 and now down to 61,000,” she said. “That is modeled on what America is doing. That’s what’s happening.”

“And I think what has been so remarkable, I think to those of us who have been in the science fields for so long,” Birx continued, “is how important behavioral change is and how amazing Americans are in adapting to and following through on these behavioral changes. And that’s what’s changing the rate of new cases, and that’s what will change the mortality going forward, because now we’re into the time period of full mitigation that should be reflected within the coming weeks of decreasing mortality.”

Speaking to Guthrie, Fauci reiterated the need to continue the distancing effort.

“I believe we are going to see a downturn in that, and it looks more like the 60,000 than the 100,000 to 200,000,” Fauci said. “But, having said that, we better be careful that we don’t say, okay, we’re doing so well we could pull back. We still have to put our foot on the accelerator when it comes to the mitigation and the physical separation.”

As The Post reported Wednesday, there are existing questions about the accuracy of the IHME model, including places in which its estimates vary from what experts are seeing on the ground. It is an estimate with a wide range of possibilities. Even after its most recent revision, the range of possible death tolls by August spans nearly 100,000 deaths — maybe as low as 30,000 and maybe as high as 130,000. That’s a broad range that could still shift depending on how Americans continue to respond to the virus.

Birx, perpetually an optimist, made the point bluntly on Thursday.

“We are impressed by the American people,” she said. “And I think models are models.”

Update: On Thursday morning, Trump echoed Birx’s assessment.