UCSF’s Dr. Bob Wachter about why he masks again

COVID-19 cases on the rise in California and Dr. Bob Wachter from UCSF posted on Twitter On Monday, he will return to more cautious behavior, putting his mask back on in indoor public areas where it may not be necessary.

“In the past month, SF has become much less mask-like,” Wachter wrote on Twitter. “If you’ve decided at this point that it’s okay to get Covid (which isn’t crazy if you’re vaxxed/boost), then it’s okay to keep your mask off in crowded indoor spaces. If you’d rather avoid Covid and have become less careful, it’s time to reconsider.”

Wachter said he is covering his face again because he prefers to avoid COVID. He said he is particularly concerned about long-term COVID symptoms and long-term risks, including damage to the heart, neurological effects and diabetes.

“I will now do 100% N95 in crowded indoor spaces,” Wachter wrote. “I prefer dining outside rather than inside, although I will eat inside in small groups (I realize it’s a risk, but it seems worth it). You have to make your own choice, but do it with an open mind eyes: there’s a lot of Covid out there.”

Wachter is the chair of UCSF’s division of medicine and has been tweeting about COVID-19 for more than two years, sharing regular updates on his view on the state of the pandemic in San Francisco and worldwide.


After peaking in January amid the ominous wave, San Francisco saw the number of cases drop significantly and the city relaxed its health mandate, eliminating the need for masks in most indoor public spaces. The number of cases is increasing again, although it is difficult to determine the extent to which state and city data is less reliable, as there are fewer test locations and more people are testing at home. Wachter said the asymptomatic test-positive rate at UCSF, where patients have to be tested for certain procedures or if they stay overnight, is a good indicator of its prevalence in the community. He said in the past week the percentage has tripled, rising to 3.4%, meaning 1 in 30 people in San Francisco are asymptomatic.

“I had slipped a bit: masking in non-crowded areas, and become less careful with: restaurants,” Wachter said. “I resume more cautious behavior.”

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