Washington (AFP) – Tests on the crew of the USS Theodore Roosevelt aircraft carrier, which was struck by an outbreak of COVID-19, found that two-thirds of sailors who tested positive were asymptomatic, a top military official said Friday.

Nearly the entire crew was tested after the coronavirus outbreak forced the nuclear-powered carrier to dock in Guam. One crew member has died.

The outbreak on the Roosevelt has allowed the Pentagon to document the impact of the coronavirus on a large military population, Joint Chiefs of Staff Vice Chairman General John Hyten told reporters.

“We haven’t really tested a whole population and we learn things from the Roosevelt about asymptomatic versus symptomatic,” he said.

As of Friday morning, 94 percent of Roosevelt crew had been tested for COVID-19, with 660 positive cases and 3,920 negative.

“It’s only 5,000 people, but it is 5,000 people of a certain demographic” that is younger and healthier than the general population, Hyten said.

Studies so far show asymptomatic patients to be between 20 and 50 percent of confirmed cases, according to Hyten, who also serves on the White House coronavirus task force.

“You look at our number. It’s almost 60, 70 percent asymptomatic,” he said.

Additionally, just over 10 percent of the positive cases had initially come back as negative in late March.

“What we learned is that those negative to positives always transitioned in the 14-day period” of quarantine recommended by health officials worldwide.

“A 14-day quarantine in individual or very small groups, followed by a test, will give us high confidence that we have a clean crew,” he said.

The Pentagon, which has stopped all movement of troops around the world, will test almost all of its forces as soon as possible to help decide how to return to normal operations.