Cases of the coronavirus in prisons and jails across the US have soared in recent weeks, even as the overall daily infection rate in the nation has remained relatively flat.

The number of prison inmates known to be infected has doubled during the past month to more than 65,000. Prison deaths tied to the coronavirus have also risen, by 73 percent since mid-May.

By now, the five largest known clusters of the virus in the US are not at nursing homes or meatpacking plants, but inside correction institutions, according to data The New York Times has been collecting about confirmed coronavirus cases since the pandemic reached American shores.

And the risk of more cases appears imminent: The swift growth in virus cases behind bars comes as demonstrators arrested as part of large police brutality protests across the nation have often been placed in crowded holding cells in local jails.

A muddled, uneven response by corrections officials to testing and care for inmates and workers is complicating the spread of the coronavirus. In interviews, prison and jail officials acknowledged that their approach has largely been based on trial and error, and that an effective, consistent response for US correctional facilities remains elusive.

“If there was clearly a right strategy, we all would have done it,” said Dr Owen Murray, a University of Texas Medical Branch physician who oversees correctional health care at dozens of Texas prisons. “There is no clear-cut right strategy here. There are a lot of different choices that one could make that are going to be in-the-moment decisions.”

The inconsistent response to the spread of the coronavirus in correctional facilities is in contrast with efforts to halt its spread in other known incubators of the virus: Much of the cruise ship industry has been closed down. Staff members and residents of nursing homes in several states now face compulsory testing.

Many meat processing plants have been shuttered for extensive cleaning.

As the toll in prisons has increased, so has fear among inmates who say the authorities have done too little to protect them. There have been riots and hunger strikes in correctional facilities from Washington state to New York.