A group of Democratic senators said Friday that they were worried about the military's ability to handle a coronavirus outbreak at the wartime prison at Guantánamo Bay, Cuba, after the Pentagon told Congress that it could maintain just four of the 40 detainees on ventilators and offered no details of how it might care for the 1,500 troops there.
"The Pentagon's response leaves doubts about the Guantánamo prison's capacity to protect military personnel and detainees from Covid-19," the 11 senators said in a statement, which included a call "to responsibly close this facility that is inconsistent with our values, does not make us safer and wastes taxpayer dollars."
The senators, led by Elizabeth Warren of Massachusetts and Jack Reed of Rhode Island, the ranking member of the Senate Armed Services Committee, wrote Defense Secretary Mark T. Esper in May seeking details on how the remote base would handle an outbreak, particularly among the older detainees and those with chronic illnesses.
The oldest prisoner turns 73 next week. The youngest is in his mid-30s.
One key concern is that, by law, prisoners at Guantánamo must receive all their medical care there, while any of the other 6,000 residents could be medically evacuated to mainland hospitals if needed.
In detailing the base's health capabilities, Matthew P. Donovan, an under secretary of defense, said the detention operation had acquired the ability to do rapid on-site testing in addition to airlifting samples to U.S. military labs.
The military acknowledged two cases of the virus on the base, in March and April, before the Pentagon ordered installations to stop disclosing any new cases for "operational security" reasons.
Defense lawyers said this week that none of the prisoners had been tested, based on calls and letters they had received from the prison since the World Health Organization declared the pandemic on March 11.
Col. Amanda Azubuike of the U.S. Southern Command, which oversees the prison but not the base, said this week that the detention operation had been able to do rapid testing since at least June, but declined to say how many prisoners or staff had been tested with either method. She said the prison tests symptomatic people and those who had come within six feet of them for more than 15 minutes.
In his response to Congress, Mr. Donovan said the prison — which is under the command of a one-star admiral and on a restricted portion of the base — checks the temperature of anybody entering the prison buildings, known as camps.
Those who typically go inside include Army guards, mostly National Guard troops on nine-month tours, Navy medical staff temporarily assigned to the prison's Joint Medical Group and resident Pentagon contract workers, such as linguists and janitors.
The Pentagon notified the senators that the prison has different medical teams for the detainees and their guards "to mitigate any inadvertent cross-contamination."
The prison has the capacity to isolate each of the 40 prisoners, including with space for four in regular inpatient rooms, two in intensive care and two more in rooms that have negative pressure and can control the flow of infectious particles.
The prison clinic has six ventilators and the ability to maintain four "Covid-19 ICU patients on ventilators at the same time," according to a fact sheet furnished by Mr. Donovan. As of July 9, the military had ordered a portable oxygen generator for the prison clinic that, meantime, had a "large number of oxygen tanks available."
Doctors who looked at the capabilities noted that the prison's Covid-19 Care Team lists only four I.C.U. nurses, far below a standard of care that requires one such nurse per ventilated patient around the clock. The team also includes three board-certified doctors but does not specifically include anyone trained to manage patients on ventilators, although the separate base hospital has a sailor who is trained as a respiratory therapist.
"They've identified equipment and rooms that they need, but the staff is not filled in," said Dr. Stephen N. Xenakis, a psychiatrist and retired Army brigadier general who commanded the Dwight David Eisenhower Army Medical Center at Fort Gordon in Georgia.
"You have got to have an I.C.U. nurse per ventilator," he said. "Even in a negative pressure room."
Mr. Donovan's reply said the prison had designated an isolated building to quarantine and triage troops with Covid-19, who can access clinical and psychologist support day and night. But the military provided the senators with no parallel information on ventilators, I.C.U. beds and medical staff.
The military declined to make available base or prison health care providers to discuss Guantánamo's measures for managing and preventing the coronavirus's spread. Colonel Azubuike said "services are in place" to treat prison staff "as required."
Pandemic health concerns have twice forced the International Committee of the Red Cross to cancel quarterly delegation trips to meet with the prisoners.
The other senators who joined the statement of concern were Patrick J. Leahy of Vermont, Richard J. Durbin of Illinois, Edward J. Markey of Massachusetts, Sherrod Brown of Ohio, Thomas Carper and Chris Coons of Delaware, Jeff Merkley and Ron Wyden of Oregon. They were joined by Bernie Sanders of Vermont, an independent who is aligned with the Democrats.
Congress has been asking questions about Guantánamo's health care infrastructure for years.
A new law in December created a full-time independent chief medical officer at the prison who answers to the Pentagon rather than the prison commander and the Southern Command.
Mr. Donovan wrote the senators that he was working on filling the job.