The US surgeon general on Sunday defended a renewed mask mandate in Los Angeles, saying other areas may have to follow and adding that he is "deeply concerned" about the Covid-19 outlook in the fall.
Dr. Vivek Murthy, who as surgeon general is a top government spokesman on public health matters, appeared on several news programs just hours after a new indoor mask mandate took effect in Los Angeles.
No other US city has returned to an indoor mask mandate, but Murthy said he expected others to follow amid a surge in the highly transmissible Delta variant of the virus.
"In areas where there are low numbers of vaccinated people, or where cases are rising, it's very reasonable for counties to take more mitigation measures like the mask rules you see coming out in LA, and I anticipate that will happen in other parts of the country," Murthy told ABC's "This Week."
After months of declining spread, the number of Covid-19 cases in the US soared by a stunning 135 percent over the past two weeks, with increases seen in nearly every state.
Los Angeles has also seen a sharp surge.
"In the last few days, we're up to almost 1,900 cases, and over 460 individuals that are now in our (intensive-care) units," Hilda Solis, a member of the Los Angeles County Board of Supervisors, told ABC.
"This is very disturbing, and of course, as responsible elected officials, we have to do something."
Persistent vaccine skepticism -- driven by misinformation -- has fueled the rise in many areas, even as health officials work to reassure the public of the vaccines' safety and efficacy.
Ninety-seven percent of those hospitalized in June were unvaccinated, according to Rochelle Walensky, director of the US Centers for Disease Control and Prevention.
Just 48 percent of Americans are fully vaccinated; the figure is 68 percent among those 18 and older.
The combination of the surging Delta variant and the lag in vaccinations has left Murthy feeling "deeply concerned" about prospects for the fall, as more people return to work and unvaccinated children return to school.
"What I worry about," he said, "is that we still have millions of people in our country who are not vaccinated. We have to still protect our children under 12 who don't have a vaccine."
Following US President Joe Biden and other administration officials, Murthy sharply criticized social media platforms for allowing Covid-19 misinformation to proliferate.
"The platforms have to recognize they played a major role in the increase in speed and scale with which misinformation is spreading," he said in a separate appearance on CNN.
"We're not seeing nearly enough progress here."