A person wears a mask while walking in the Grand Central Terminal on July 27, 2021 in New York.
Spencer Platt | Getty Images
The Centers for Disease Control and Prevention recommended Tuesday that fully vaccinated Americans begin wearing masks indoors again in areas with high Covid-19 transmission rates as national infection levels rise again. .
The CDC Director, Dr. Rochelle Walensky, told reporters Tuesday that the masks should be worn in public, in indoor environments by everyone, including fully vaccinated people, in areas “with a substantial and high throughput.”
But what exactly is “high” or “substantial,” transmission, and where are the areas of interest to the CDC?
The agency uses a two measures to group U.S. counts into four levels of community transmission: the number of new cases per 100,000 population and the percentage of Covid tests that were positive last week.
If a county reported 50 to 100 cases per 100,000 inhabitants over a seven-day period or has a positivity rate of 8% to 10%, it enters the “substantial transmission” level, while those reporting 100 cases or more per 100,000 or have a positivity rate of at least 10% are labeled as “high transmission”. These are the two groups for which the CDC recommends a mask.
The CDC says 1,495 counters are in the highest transmission group and another 548 counties are at the “substantial” level – areas where masks should be worn in restaurants, businesses, any public space. These combined counts make up 225 million Americans, according to a CNBC analysis of CDC data, or about two-thirds of the U.S. population.
Accounts with moderate transmission, which are not subject to CDC warning, make up another 31% of the population while just over 1% of Americans live in accounts with low transmission rates, according to the CDC criteria, which is currently in effect on July 27th.
Federal health officials still believe that fully vaccinated individuals represent a very small amount of transmission. However, the more contagious delta variant means that some vaccinated people could carry higher levels of the virus than was previously understood and potentially transmit it to others as easily as unvaccinated individuals, Walensky said.
There are at least three states where each county falls under the CDC’s mask council: Florida, Louisiana and Arkansas.
The Covid delta variant is one of the most infectious respiratory diseases ever seen by scientists, Walensky said last week. The variant is highly contagious, in large part because people infected with the delta strain can carry up to 1,000 times more viruses in their nasal passages than those infected with the original strain, according to the news data.
“The delta variant is more aggressive and much more transmissible than the strains that circulated earlier,” CDC director Dr. Rochelle Walensky, in a briefing Thursday. “It’s one of the most infectious respiratory viruses we know of, and one I’ve seen in my 20-year career.”
The CDC’s guidance is only a recommendation, and leaves it to states and local officials to decide to reintroduce its mask rules for certain people. Some areas have begun reintroducing mask mandates in recent weeks.
Dr. Natasha Bhuyan, a family physician with One Medical in Phoenix, Arizona, said she is advised to wear masks to her patients since the delta variant is so much more contagious than other variants.
“We know that when you are vaccinated, you are much less likely to be rejected or die by Covid,” he said. “But even if you are vaccinated, while rare you can still get Covid and you can still be contagious and pass Covid to other people.”
Phoenix is in Maricopa County, which is in the highest transmission category in the community.
“Delta has changed our thinking about when people should wear masks,” Bhuyan adds. “It’s not going to last forever. When we get the vaccination rate and the Covid case rate down, people will be able to take off their masks.”
CNBC Berkeley Lovelace Jr. contributed report.
Correction: This article has been updated to remove Hawaii as one of the states where each county meets the CDC’s mask council. Kalawao, County, population 86, has low transmission rates.