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F ACED WITH a pandemic, officials rush to close any place that threatens to become a centre of transmission. If fewer people mingle inside cruise ships, schools, churches or retirement homes then the risk of mass infections falls. Yet for more than 2m Americans squeezed into jails and prisons, along with many staff, a shutdown is not an option. Instead, such places risk becoming hotspots for disease. In 1918 the Spanish flu raged through San Quentin prison in California, infecting 500 of its 1,900 inmates in just two months.

Anxiety is rising by the day. The sheriff of Harris County, Texas, has likened his huge jail to “a perfect incubator” for covid-19, saying an outbreak would spread like “wildfire”. Inmates at an immigrant-detention centre in New Jersey have launched a hunger strike to demand soap. At Rikers Island, in New York, prisoners this week refused to leave their dormitories, worrying about infections. Tom Dart, sheriff of Cook County, who runs a large jail in Chicago, warns he is “juggling with impending disaster”. Some prisoners have the virus, but he lacks tests for checking others or even protective gear for staff.

“Universities and hotels you can close. I’m left with people I can’t send home,”, says Sheriff Dart. Instead he improvises. He clumps new arrivals in cohorts by the day they come in, hoping to isolate potentially sick ones for at least a week to prevent any infection spreading. Tents for quarantine are now going up in place of a mental-health centre. Staff take inmates’ temperatures, quiz them about sickness in the family and spray food trays with bleach water more often than before.

Such efforts are well-meant but inadequate. The virus is already spreading behind bars. Prisons in every state now ban regular visitors. In 15 states even lawyers are blocked. As staff and volunteers who provide education, therapy and other services also stay away, another risk is that morale will fall, to be replaced by mounting fear and frustration. That bodes ill for good order. In Italy similar efforts to contain the virus this month provoked at least 25 prison riots and several deaths.

Inmates are often packed close and obliged to buy their own soap—seen as a luxury, not a basic need—from meagre earnings. They will struggle to fend off infection. Pam Oliver, a sociologist who studies prisons in Wisconsin, calls the lack of hygiene “extremely dangerous”. The current crisis at least is raising public awareness of “severe overcrowding and unsanitary conditions” for those locked up, says Inimai Chettiar, of Justice Action Network, which campaigns for reform.

In Harris County some pregnant inmates have been released. Those protesting in Rikers want detainees aged 50 or older sent home. Ohio’s chief justice has said that people at highest risk of infection must be isolated outside jails. Ms Oliver notes that older inmates are both at risk and pose little threat, as they are unlikely to reoffend. A bill, HR 4018, which was unanimously passed by the House last year and is waiting to go before the Senate, would make it easier for elderly prisoners to serve the final third of their sentences at home.

Another effort in many states aims to prevent people entering jails in the first place. Sheriff Dart in Chicago says daily arrivals have recently fallen by nearly half, from 100, as police issue more citations and arrest fewer offenders. That is becoming common in dozens of counties and cities. In Baltimore the state attorney, Marilyn Mosby, has told prosecutors to stop charging non-violent offenders such as those caught dealing drugs, trespassing or illegally selling sex. In Los Angeles, where 17,000 are in jail on an average day, officials are aiming to get the population down by 2,000. Daily arrests there have dropped from 300 to 60, says the sheriff.