Hawaii officials dealing with the rapid spread of COVID-19 at the Oahu Community Correctional Center are finding out what many of their mainland counterparts already know: Once the virus has entered a prison, it’s near impossible to contain it without immediate action to ramp up testing and disperse the inmate population.

Tight quarters, limited access to sanitary supplies and a large population of older inmates with chronic illnesses make prisons particularly vulnerable to the spread of highly infectious diseases. Researchers at Johns Hopkins Bloomberg School of Public Health reported last month that COVID-19 case rates were 5.5 times higher and escalating much more rapidly in prisons than in the general U.S. population.

As in Hawaii and other states, one of the remedies to limit infections has been the release of certain categories of prisoners to make more room for physical distancing. California’s Department of Corrections and Rehabilitation, which oversees 35 adult prisons, has already released approximately 10,000 inmates since mid-March and may release up to 8,000 more by the end of August.

As of Thursday, there were 96,881 incarcerated persons in California’s prisons, with 1,036 active cases of COVID-19. In all, there have been 9,135 confirmed cases and 53 deaths among inmates, according to CDCR. Additionally, among employees, there have been 2,235 confirmed cases and nine deaths.

Other measures taken by the California prison system include activating a centralized command of custody and health care staff, providing masks and hand sanitizer to all staff and inmates, suspension of intake from county jails, reducing the number of people who use common spaces at the same time, transferring inmates out of dorms to individual cells and erecting tents to serve as alternate housing and isolation/quarantine options.

Dr. Stefano M. Bertozzi, a professor of health policy and management at the University of California, Berkeley, School of Public Health, was a member of a team of medical advisers who visited the state’s oldest prison, San Quentin, in mid-June when only 14 COVID-19 cases had been reported. As of Thursday, there were 2,233 confirmed cases, and now Folsom is teetering toward a similar explosion of infections.

Bertozzi, who is associated with Amend, a group that works to improve inmate health, said he didn’t have information on Hawaii’s situation, but that “it’s really important to look at the different levels of risk depending on the facility.” Speaking via a Zoom video call from California, he said prisons at far higher risk for the rapid spread of COVID-19 feature collective housing in dorms or cellblocks with bars where inmates spend hours together breathing the same air — “a perfect setup for one of these super spreading events” — versus facilities where the population is spread out in cells with doors, walls and proper ventilation.

In the case of the San Quentin outbreak, according to Bertozzi, there were only 100 individual cells to house the 620 inmates from a five-level cellblock who needed to be quarantined.

“They didn’t act quickly enough to get them in hotels or dorm rooms or some other facility where they could have, or a cruise ship. They were trying to be creative, but it didn’t happen; they didn’t get them out of there in time and it ended up infecting the vast majority of the people in the cellblocks,” he said.

Bertozzi cited three essential actions to limit prison outbreaks in their early stages: “cohorting” of inmates and staff; widespread testing with quick turnaround; and releasing prisoners, especially those at high risk of serious health complications.

“You want to divide that prison into a bunch of small prisons, even if it’s within the same prison,” he said. “You want pieces of the prison to only interact with themselves and not be interacting across cohorts. So you want prisoners who are in a particular part of the prison to stay in with those prisoners and not be crossing over, and you want the staff who interact with those people to only work with those people. And when you have somebody who has to cross over, then they take extreme precautions. They’re tested very frequently, ideally every day that they cross over, and they use more stringent PPE (personal protective equipment) … .

“And you also really need to work on social distancing and mask wearing for everybody in the prison but especially for the staff, because that’s the route of introduction into the prison.”

Testing turnaround is a problem across the country, but it’s vital to preventing transmission, Bertozzi added. “You really need to get the testing labs to put these tests at the top of priority list because there’s no place that is at higher risk of a rapid spread than a prison setting. Where else do you have dorms with 200 men?”

And finally, “letting people out … that’s really important.”

The good news for California, Bertozzi noted, is that the number of active cases in custody has fallen since early July, although that could change if the Folsom outbreak gains steam.