Detained immigrants have begun hunger strikes in recent weeks amid fears that the virus could sweep through packed detention facilities, and several courts have ordered the release of individual detainees.

Cases surge in an Ohio prison, making it a top U.S. hot spot.

A state prison in Ohio is now the largest reported source of virus infections in the United States, according to a New York Times database, continuing a trend of fast-moving outbreaks behind bars.

Ohio officials said Sunday that at least 1,828 inmates — almost three-quarters of the prison population — had tested positive at the Marion Correctional Institution, a minimum- and medium-security prison about an hour’s drive north of Columbus. That’s more than the number of known cases at a meatpacking plant in South Dakota and an aircraft carrier docked in Guam.

About one out of five confirmed virus cases in Ohio is now connected with the state’s prison system, according to statewide figures. The Department of Rehabilitation and Correction said that as of Sunday, at least 2,400 inmates in the system had tested positive, and seven had died of either confirmed or suspected Covid-19 infections.

No deaths have been reported among the prisoners in Marion, but one staff member at the facility has died, and 103 employees have tested positive. The prison announced its first positive case, of an employee, on March 29.

Despite warnings from health officials and attempts to release some inmates to avoid outbreaks, jails, prisons and detention centers have emerged as major coronavirus spreaders. As of Monday, four of the 10 largest-known sources of infection in the United States were correctional facilities, according to Times tracking data.

And even those numbers are most likely a vast undercount, because some state and local agencies have not released information about cases behind bars, and others, including the federal Bureau of Prisons, are not testing everyone who falls ill. In contrast, the Ohio corrections department said it was testing aggressively inside prisons where the virus has been confirmed, extending tests even to prisoners who were not showing symptoms.