WASHINGTON (Reuters) – The U.S. government’s top infectious disease expert said on Tuesday there were “glimmers” that social distancing efforts to slow the spread of the coronavirus were having an impact, even though the nation was still in a very dangerous situation.

“We’re starting to see glimmers that that is actually having some dampening effect,” National Institute of Allergy and Infectious Diseases Director Anthony Fauci told CNN in an interview. “But that does not take away from the seriousness … We clearly are seeing cases going up.”

Fauci’s comments came after the United States endured its deadliest day yet on Monday with 575 coronavirus-related fatalities. U.S. officials want to build hundreds of temporary hospitals across the country as existing medical centers have come under siege from the coronavirus outbreak.

The number of U.S. dead has now climbed past 3,000, more than the number who died in the attacks of Sept. 11, 2001, as confirmed cases of COVID-19 infections rose to more than 163,000, according to a Reuters tally of official U.S. statistics.

Fauci cautioned that, while stay-at-home restrictions were starting to produce some results, Americans remained at risk.

“We clearly are seeing cases going up. People in New York

are in a difficult situation,” he said. “We are still in a very difficult situation. We hope and I believe it will happen, that we may start seeing it turn around, but we haven’t seen it yet.

“We really have to hang in there and abide by the mitigation strategies. We do believe it’s working.”

(Reporting by Doina Chiacu and Tim Ahmann; editing by Susan Heavey and Bill Berkrot)