The correctional complex on State Road in Northeast Philadelphia (Kimberly Paynter/WHYY)

In late May, Philadelphia jail officials set out to test every person at the city’s four correctional facilities, whether or not they were showing symptoms of the coronavirus. The results are now in, adding to mounting evidence that COVID-19 spreads covertly in close-quarter settings.

Over the past two weeks, 6% of incarcerated people without symptoms tested positive — or 220 out of 3,695 inmates, officials told Billy Penn.

The experiment was conducted several weeks after the viral surge peaked in the region in late April. Only 17 people in custody refused to participate.

Cases among people without symptoms are spread between all four city facilities on State Road, according to Prison Commissioner Blanche Carney, who said everyone yielding positive results was placed in strict quarantine for two weeks.

The city’s jail population still remains on edge, now three months into a lockdown that requires distressing conditions intended to curb the virus’ spread.

The asymptomatic infection rate in Philly jails may change, as dozens of results have yet to come back from the lab. But it’s lower than found in other congregate settings. In April, officials in suburban Montgomery County tested nearly 1,000 incarcerated people and found about 11% carrying the virus, with only half a dozen showing any symptoms.

Philadelphia has been testing incarcerated people with symptoms since March. A total of 197 positives were reported prior to the universal sweep, about 75% of symptomatic inmates tested.

It has been weeks since the city has reported more than a single person in jail showing coronavirus symptoms.

Critics said the true number of cases behind bars was likely much higher. The American Civil Liberties Union of Pennsylvania and other groups sued the jails in April over the lockdown conditions and the lack of testing. One of the plaintiffs is a man who reported symptoms in jail and says he was still refused a test.

Prison Commissioner Carney said she wasn’t surprised by the universal results. She cited the jails’ quick adoption of shelter-in-place measures, restricting movement and contact between inmates. Still, cases erupted for weeks through March and April before they began to decline.

Does she think the rate would have been even higher if they had conducted mass testing during the peak of the outbreak, as criminal justice advocates and civil rights attorneys had asked them to?

“Not necessarily, but it would have been helpful,” Carney said, citing the shortage of tests citywide at the time. “But the reason I think we are where we are now is because we put those measures in place.”

Low case count or not, the system-wide lockdown means people remain in their cells for more than 23 hours a day, and a single positive case on any given cell block means a more intense two-week isolation for every resident on that block.

“The population remains concerned with when we’re going to transition back to a sense of normalcy,” Carney said. “The anxiety is still there.”

The commissioner said there is no timeline on relaxing lockdown protocols yet.

The city will continue to test every new jail resident and enforce mandatory quarantine upon release. But Carney said they won’t test upon release — another source of scrutiny in the jail’s early handling of the virus.

Over 1,300 were discharged in the weeks after the outbreaks as people inside were falling ill, potentially allowing returning citizens to unknowingly take the virus home to their families.

Said Carney: “To test on release would be redundant, because we’ve already cycled through the population we have in custody.”

Max Marin (he/him) was Billy Penn's investigative reporter from 2018 to 2021. A graduate of Temple University, he has produced award-winning journalism on local politics, criminal justice, immigration...