Officials responsible for American prisons and jails say they are prepared for the ongoing coronavirus outbreak, while advocates for the incarcerated worry it could cause “devastating effects” if it reaches correctional facilities.

More than 2.1 million people were incarcerated in a prison or local jail at the end of 2016, according to federal statistics. Those people packed into these facilities — who research has found are more likely to have had chronic conditions or infectious diseases — do not include the regular flow of officers, other staffers, attorneys and visitors who make their way in and out every day.

“You have an artificial environment which is at a high risk for transmission,” Josiah D. Rich, a doctor and professor of medicine and epidemiology at Brown University who co-founded the Center for Prisoner Health and Human Rights, said in an interview.

The virus is believed to spread between people who are in relatively close contact, though it could also be transmitted via surfaces or objects that have been contaminated, according to the Centers for Disease Control and Prevention.

The federal Bureau of Prisons — which has more than 146,000 inmates in its custody, along with more than 28,000 in private or other facilities — has “a screening tool in place for use in the event an inmate or staff member is exposed or symptomatic,” a spokesperson said in a statement. The bureau said its system has no coronavirus cases, which was echoed by the Texas correctional system and others.

In Washington state, which is home to an ongoing outbreak at a nursing facility, corrections officials said they have plans in place to prevent the spread of infectious diseases. The Florida Department of Corrections said in a statement that it “is fully prepared to handle any potential cases” of coronavirus and that visitations are continuing as normal.

In New York state, the Department of Corrections and Community Supervision said two staff members were staying home because of the outbreak. One of them had symptoms but tested negative for covid-19, the disease caused by the virus, while the other “was near someone who may have the virus and so is staying home as a precaution but has not exhibited any symptoms,” a spokesperson said.