It spread like a ghost. There were signs that the virus has been spreading through prisons, but then again, few people were manifesting symptoms.
“We weren’t always able to pinpoint where all the cases were coming from,” said Annette Chambers-Smith, director of the Ohio Department of Rehabilitation and Correction.
So they began mass testing the prison population -- and when the results came in, they were surprising.

COVID-19 can spread like wildfire in prisons. A crowded population, where social distancing is impossible and hygiene is often a luxury, seems like a great environment for the virus to thrive. Add in the fact that US prison populations are now aging and around half of all prisoners are suffering at least one chronic ailment, and things get even worse. Prisons can be important disease hotspots and understandably, authorities are increasingly looking at mass testing prisons.
Testing has been deployed (to an extent) in four state prison systems: Arkansas, North Carolina, Ohio, and Virginia, and the results showed some pretty unexpected stats. Out of the 4,693 tests, 3,277 inmates tested positive for the coronavirus -- and out of them, 96% were asymptomatic.
It's important to note that some people who were asymptomatic when diagnosed may go on to develop symptoms later on, but it's still a massive figure, suggesting that the disease is largely passed on by silent carriers.
This may have important implications outside of prisons, as well.
“It adds to the understanding that we have a severe undercount of cases in the U.S.,” said Dr. Leana Wen, adjunct associate professor of emergency medicine at George Washington University, told Reuters of the findings. “The case count is likely much, much higher than we currently know because of the lack of testing and surveillance.”
We will have more information on this soon enough, as state prisons in Michigan, Tennessee, and California have also begun mass testing, including tests on some inmates who show no sign of illness. For now, the preliminary results in Tennessee and Michigan also seem to suggest that a large part of the positive cases don't show any symptoms at the time of testing.

COVID-19 poses threats for prisons all over the world. In the UK, recent reports suggest that thousands of prisoners are already infected, and similar concerns have been voiced in other of the world.
Several countries (most recently, France) have already temporarily released some low-risk prisoners and delayed some sentences, which could be an important option to consider in the US as well.
The US has the highest incarceration rate in the world, accounting for 22% of the world's prisoners (despite having around 4% of the world's population). At the end of 2016, the Prison Policy Initiative estimated that in the United States, about 2,298,300 people were incarcerated.