White House health advisor Dr. Anthony Fauci said he has "no doubt" that Americans who aren't wearing face masks, especially in large crowds, are increasing the risk of spreading the coronavirus.
"When you have crowds of people together and you have the lack of wearing a mask that increases the risk of there being transmissibility. I have no doubt about that," he said during an interview Friday on CNBC's "Halftime Report." "When we see that not happening, there is a concern that that may actually propagate the further spread of infection."
The comment came a day after CDC Director Robert Redfield told lawmakers he was worried Americans aren't following the agency's advice as states begin to reopen after shuttering businesses and limiting activities as part of social distancing measures intended to curb the spread of the virus.
Crowds of people, some without masks, have been seen in recent weeks at protests, over the Memorial Day holiday and, Redfield noted, at the SpaceX launch over the weekend.
The CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain.
"We will continue to message as well we can," Redfield told the House Appropriations Committee during a hearing on the coronavirus. "We're going to encourage people that have the ability to require to wear masks when they are in their environment to continue to do that."
Fauci, director of the National Institute of Allergy and Infectious Diseases, also said Friday that the coronavirus outbreak in the U.S. appears to be going in "the right direction" despite a few "blips."
The coronavirus, which emerged about five months ago, has sickened more than 1.8 million people and killed at least 108,211 across the United States, according to data compiled by Johns Hopkins University. While cases are slowing in hot spots such as New York, they have been on the rise in places such as Florida, Texas and Arizona.
The National Institutes of Health has been fast-tracking work with biotech firm Moderna on a potential vaccine to prevent Covid-19.
Fauci said earlier this week that there are at least four trials for potential vaccines that he is either directly or indirectly involved in. He said that by the beginning of 2021 "we hope to have" a couple million doses.
On Friday, Fauci said he hopes Americans won't be "reluctant" to take the vaccine that could be potentially lifesaving.
"Unfortunately there's ... kind of a trend of anti-science and with that anti-vaccine in this country, which is really unfortunate, because for the most part it's really based on misinformation," he said. "But I would hope that as we get a vaccine available for us here in the United States and even worldwide, that given the potential and real seriousness of this outbreak now and in the future, that people will not be reluctant to take a vaccine that's potential is lifesaving for them."