Prisons and jails number among the top hotspots for coronavirus outbreaks in the US - and new Harvard University research suggests that for every one person who goes into a jail, another two people in the communities they return to develop COVID-19.
By the end of last month at least 78,526 people had tested positive for coronavirus in US prisons.
It's no surprise that coronavirus can spread like wildfire in jails and prisons where hundreds or thousands of people live in close quarters and share communal bathrooms and dining areas.
But the Harvard study found that the impact of these outbreaks is not confined to the prison walls.
Instead, the high turnover rate with which people enter and exit jails and return to their communities drive higher coronavirus cases in their counties, a phenomenon that add to the disproportionate effect the pandemic is having on black, Hispanic and poor Americans, the Harvard study found.
At least 350 prisoners and staff at Cook County jail in Illinois contracted coronavirus by April. New research suggests people who came into. and out o the massive jail may be linked to more than 15% of infections in Chicago (which is located in Cook County)
Prisoners who tested positive for coronavirus at Cook County jail were moved to an isolation area within the facility (pictured)
It's ultimately a function of the way that jails work in the US.
About 600,000 people are incarcerated in prisons each year in the US, but 10.6 million people are booked into jails, according to the Prison Policy Initiative.
Jails mostly hold people who have been arrested but not convicted, and the vast majority of them won't be.
That means that they're held for hours, or perhaps days, then released.
It only takes one infected person to introduce coronavirus to a jail population where like an ember in draught conditions, the virus can spread like wildfire.
And it only takes a short amount of time in an area of confined viral activity for someone to get infected before carrying it back out the jail's doors to the general population.
'You can think of cycling people through jail as having a multiplier effect' on the spread of coronavirus, Eric Reinhart, a Harvard anthropology PhD candidate and study co-author told The Harvard Gazette.
That's exactly what he and his colleagues found happening in Cook County, Illinois, stemming from its jail.
They counted up bookings, releases and coronavirus test results of people who went into and out of the Cook County Jail in March and compared them to changes in the number of new positive tests in