Statistics released by the city on Monday pointed to an outbreak that was still small but quickly growing. The average number of newly reported cases was 224 a day, a relatively tiny figure for a large city, but a 240 percent increase over two weeks. Eighty-two people were hospitalized with Covid-19, nearly double last Monday’s number. But the death toll, which typically lags weeks behind case and hospitalization totals, had not ticked up so dramatically in the weeks since it had reached the horrific number of 5,000.
In the low but rapidly rising numbers, the city’s health officials saw a familiar warning.
“I remember seeing that when Delta was on the horizon,” Dr. Cheryl Bettigole, the city’s health commissioner, said in an interview, describing the ominous days last year when Philadelphians were finally enjoying a respite from Covid-19 while she and her colleagues watched a new variant wreaking death and illness in Europe. “It was hard to get people to pay attention,” she said.
When Dr. Bettigole and other health officials began assembling a series of metrics that would determine which mitigation policies should be in place at which times, the experience of Delta was on her mind, she said. So they decided that a 50 percent jump in daily infection counts over 10 days — what she called “the most reliable measure we’ve seen in previous waves” — plus a rise in the absolute number of infections over 100 or hospitalizations over 50 would automatically trigger an indoor mask mandate.
As critics of the order are quick to point out, Philadelphia’s guidelines differ from those of the federal Centers for Disease Control and Prevention. The latest C.D.C. guidelines place more emphasis on hospital admissions and occupied hospital beds, which are measures of the strain on health care systems rather than direct gauges of infection risk; like deaths, those metrics tend to lag several weeks behind the trend in new cases. By the C.D.C.’s definition, Philadelphia was still solidly in the “low” category when the mask mandate was reinstated.
“What is the argument to go against the C.D.C., to go against Dr. Fauci?” asked Allan Domb, a real estate mogul who sits on the Philadelphia City Council. “This is hard to understand when all these other institutions are saying it’s not necessary.”
Dr. Bettigole acknowledged the divergence, but insisted that the decisions were being made based on the specific conditions in Philadelphia, a city with a large population in poverty and one where Black communities have been particularly hard hit by the virus.