People wearing face masks walk on Hollywood Boulevard during the coronavirus disease (COVID-19) outbreak in Los Angeles, California, the United States, on March 29, 2021.

Mario Anzuoni | Reuters

From Los Angeles to Massachusetts, local officials across the country are urging Americans to wear masks again as the Delta variant rips across the US

Several California and Nevada counties are now advising all residents to wear masks in public indoor spaces, regardless of whether they are vaccinated or not. Local leaders in at least three other states have reintroduced mask mandates, issued face-covering recommendations, or threatened the return of strict public health limits for all residents – despite federal health guidelines that in most cases, vaccinated individuals do not use these protocols must follow the settings.

“A surge in the number of cases was not unexpected as the community began to reopen fully,” Jennifer Sizemore, spokeswoman for the southern Nevada health district, told CNBC in an email. Clark County, home of Las Vegas, tightened its mask recommendation last week after Covid-19 cases and deaths rose 50% in the previous week. A total of 4,599 new infections and 33 coronavirus-related deaths were reported last week, according to data from the Centers for Disease Control and Prevention.

Covid infections are rising again in the US after months of falling cases, new cases have risen 55% since last week to an average of 37,000 new cases per day in the past seven days, according to a CNBC analysis of data compiled by Johns Hopkins University .

The CDC relaxed its Covid guidelines on masks for fully vaccinated individuals on May 13, stating that they do not need to use them or practice social distancing in most environments. CDC director Dr. Rochelle Walensky told lawmakers at a Senate hearing Tuesday that the agency was actively reviewing its mask and other public health guidelines as the virus and pandemic evolve, especially as scientists learn more about the Delta variant and how it is doing Keep vaccines against it.

“A lot has changed since May 13,” said Walensky. “We now have a variant in circulation in this country that was 3% (of new cases) at the time and is now 83% and much more transferable.”

The Delta variant is spreading across the country, especially in areas with low vaccination rates, she said. Nearly two-thirds of counties in the US have vaccinated less than 40% of their residents, “which is what enables the emergence and rapid spread of the highly transmissible Delta variant,” leading to an increase in hospital admissions and deaths, she said.

This is gradually becoming apparent in Nevada, which, according to CDC data, has only fully vaccinated 43.5% of its population. Clark County recorded 641 new Covid hospital admissions last week, 23% more admissions than the previous seven days. Despite the resurgent outbreak in the Las Vegas area, Sizemore said the county’s vaccination rate has remained at just under 42% for the past two weeks.

“However, the community’s vaccination rate has slowed and unvaccinated people are not taking recommended precautions, including wearing masks and continuing to practice social distancing,” Sizemore said.

Nevada isn’t the only state that is stepping up its mask guidelines. On Friday, seven counties in California’s Bay Area recommended the use of masks indoors for a full mandate. The California city of Berkeley also called for the continued use of masks.

Further south, Los Angeles County restored its indoor public mask mandate on Saturday. The county initially lifted the mandate on Thursday when the state formally withdrew a number of executive measures to contain the spread of Covid.

White House senior medical advisor Dr. Anthony Fauci said Los Angeles County’s new mask mandate could serve as a prototype for other regions with high rates of infection. He said he expected schools and businesses to continue enforcing their own mask policies to protect against the Delta variant.

“If you want to be even more secure despite being vaccinated, you should wear a mask indoors, especially in crowded places,” Fauci said in an interview with CNBC’s Closing Bell. On Wednesday.

In Massachusetts, Provincetown officials advised everyone on Monday to resume wearing masks indoors after the July 4 celebrations resulted in an outbreak of new cases.

In Orleans Parish, Louisiana – where the CDC reported 560 new coronavirus cases last week – New Orleans Mayor LaToya Cantrell authorized a consultation on indoor masks on Wednesday to help curb the spread of the Delta variant. And New Jersey Governor Phil Murphy told CNBC’s Squawk Box on Tuesday that he wanted to avoid reinstating a mask mandate and instead press for residents to get vaccinated.

“Right now, I hope we don’t have to,” Murphy said. “If we have to, we will.”