WASHINGTON (AP) — The Navy destroyer USS Kidd was heading east across the Pacific from Pearl Harbor when it added an unusual twist to its transit — a quarantine-and-isolation drill. The practice was part of a new protocol built on lessons from a coronavirus outbreak aboard an aircraft carrier soon to be sidelined with sickness.

“That ... actually helped us quite a bit to prepare for what was to come,” the Kidd’s commanding officer, Cmdr. Nathan Wemett, said in a telephone interview Thursday from aboard the ship.

What was coming a few weeks later for Wemett and his crew of about 330 was a COVID-19 outbreak that is just the second aboard a Navy ship at sea. Nearly one-quarter of the Kidd's crew has the virus. Still, lessons learned from the outbreak aboard the aircraft carrier, the USS Roosevelt, has allowed the Kidd to avoid a similar spectacle of crisis.

The Kidd's circumstance is not completely comparable to that of the nuclear-powered Roosevelt, whose crew of 4,900 is far larger and whose presence in the Pacific is a bigger symbol of American power. But Wemett says his ship benefited from information and guidance derived from the unfolding and unforeseen disaster aboard the aircraft carrier.

For example, on April 20, the Kidd received new medical guidance on additional symptoms to be watching for as indicators of possible coronavirus.

“That drove us to report our first case" that same day, Wemett said. The ill sailor was medically evacuated to a medical facility in San Antonio two days later for testing, and the following day a positive result was reported. By this time the ship was putting its at-sea drills to use by placing some crew members in isolation.

Even before the first test result was known, the Navy assembled a medical team in the United States and dispatched it to the Kidd. The team leader, Cmdr. Michael Kaplan, the director of medical services at Naval Hospital Jacksonville in Florida, said he was not standing by in anticipation of such a mission.

“We had no heads up whatsoever,” Kaplan said.

But the team was on its way in a few hours and arrived aboard the Kidd by helicopter the same day. By evening the doctors had tested about 25 people, and within 24 hours nearly a quarter of the crew had been tested. The Navy also diverted an amphibious assault ship, the USS Makin Island, to provide additional support to the Kidd. The Makin Island has fully equipped medical facilities, including an intensive care unit.

Kapan' said his team also made a point of testing sailors without coronavirus symptoms, drawing on the Roosevelt experience, which initially tested only those with symptoms, not realizing that asymptomatic people can be transmitters of the virus. Kaplan had the asymptomatic cases isolated on board.

“We didn't know how long it would take to get back on land, and we wanted to do everything we could to try to minimize the spread on the ship,” Kaplan said.

As of Thursday, 78 members of the Kidd's crew had tested positive. None is hospitalized.

Not all aspects of the medical and operational response taken aboard the Roosevelt are known publicly, and that entire episode is now under investigation, including questions about how the virus got aboard in the first place. Just over 1,100 members of the Roosevelt crew have tested positive, and one died of complications from the disease. The Roosevelt's skipper, Capt. Brett E. Crozier, was fired for distributing a letter pleading for faster Navy action to protect his crew, and the official who ordered his removal from command, Thomas Modly, resigned a few days later as the acting Navy secretary.

At the outset of the Roosevelt’s problem, senior Navy officials appeared to underestimate their ability to contain it and keep the warship from being sidelined.

Touting the Navy’s response, Modly told reporters on March 24, two days after the first case was confirmed: “This is an example of our ability to keep our ships deployed at sea, underway even with active COVID-19 cases.”

In contrast, the Kidd ended its Central America mission shortly after getting its first coronavirus case, based on a plan made in advance by the U.S. Navy 4th Fleet organizers of the counterdrug operation. Once a ship had a certain number of symptomatic sailors, it was to head for the nearest appropriate U.S. port. Wemett declined to be more specific than to say the triggering number was less than 10.

The Kidd headed for San Diego, where it arrived Tuesday and moved most of the crew ashore to off-base housing.

The paths of the Kidd and the Roosevelt diverged in a more literal sense. They initially deployed together on Jan. 17 after the Kidd, home ported at Everett, Washington, joined up with the Roosevelt and the rest of its strike group in San Diego. But the Kidd made it no further than Hawaii, ordered to break off from the strike group and head east again to participate in the Central America counterdrug operation. The Roosevelt and the rest of its strike group, meanwhile, headed to East Asia.