Anthony Fauci
"We're in for a whole lot of hurt," warned the nation's top infectious disease expert.
He told the BBC the effectiveness of coronavirus vaccine could be known before the end of this year.
The president threw face masks to the crowd, but did not wear one himself.
Currently there are entire countries with fewer active cases than the White House.
Several hospitals in the north of England are already using the experimental treatment given to the US president.
Health experts at the University of Washington said 70,000 lives could be saved if people were scrupulous about wearing masks.
US infectious disease expert said he "wouldn’t have imagined in my wildest dreams" that people would threaten him over public health principles.
The director of the World Health Organization urged people to practice “the basics of public health" to stop outbreaks of Covid-19.
Frustrated with his low approval ratings, the president is once again leaning in to hydroxychloroquine as a Covid-19 treatment.
"It can only be my personality, that’s all," Trump said at a news conference where he lamented his plunging popularity.