The American Civil Liberties Union concludes in a new report that COVID-19 could spread rapidly in U.S. jails, leading to higher death tolls than the models touted by the Trump administration expect.

The activist group’s report is based on an earlier model, which it created with researchers from Washington State University, the University of Pennsylvania and the University of Tennessee. It found that reductions in arrests and speedier releases of prisoners would reduce COVID-19 deaths in Allegheny County, Pa. 

Predictions that model the U.S. spread of COVID-19 based on its transmissions in other countries could dramatically underestimate the virus’ toll because of the large population in the U.S. confined to jails and prisons, the authors say.

In the new report, the ACLU expanded the earlier study to include 1,242 jurisdictions with jail populations of at least 100 people. Those jurisdictions altogether cover about 90 percent of the U.S. population.

Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases, said last month he expected 100,000 to 200,000 Americans to die of COVID-19. More recently, President Trump has said it will be in the range of 50,000 to 60,000 people. The administration has relied on a model created by the University of Washington’s Institute for Health Metrics and Evaluation. Those models trust the spread of COVID-19 in the U.S. will mimic transmissions in other countries despite variations in political responses to the pandemic. 

But the ACLU says that if local governments continue to send people to jails, and do not protect the incarcerated, COVID-19 U.S. deaths could approach 375,000.

That estimate does not account for federal prisons or immigrant detention facilities. But jails — facilities that hold people awaiting trial or with sentences less than a year — are particularly perilous because of churn. According to the Bureau of Justice Statistics, 10.7 million people are put in jail each year for an average stay of 25 days. 

About 655 out of every 100,000 people in the U.S. are incarcerated, according to the World Prison Brief, a project of the University of London. In Italy, by contrast, 102 people out of every 100,000 are incarcerated. In South Korea, it’s 106 per 100,000.  

The ACLU calls U.S. jails an “Achilles heel” in combating the pandemic. “Incarceration makes it impossible to engage in the self-protective social distancing measures that public health officials are recommending,” said Brooke Watson Madubuonwu, an ACLU data scientist.

Incarcerated people are also more likely to suffer from serious health problems that can exacerbate the virus. The ACLU wants local officials to adopt a number of interventions in order to reduce the incarcerated population in light of the pandemic. Among them, it wants judges to void or suspend some outstanding arrest warrants, prosecutors to decline to charge people accused of petty crimes, and sheriffs to release vulnerable prisoners.

In addition to the ACLU, some epidemiologists have recently questioned the accuracy of initial models on the virus’ fatality rate and the methods of the University of Washington’s institute. 

The institute did not immediately reply to a request for comment about the ACLU report.

Meanwhile, some governors, prosecutors and police departments have rejected efforts to reduce the jail population. 

Republican Gov. Greg Abbott of Texas, for example, issued an executive order in March blocking some early releases on bail, while Leon Cannizzaro, a Democratic district attorney in New Orleans, also resisted efforts to release prisoners early to protect against the disease.