The goal is to keep ships at sea as “Covid-free bubbles.”

As the USS Theodore Roosevelt left Guam on Thursday to resume a deployment interrupted for more than two months by an outbreak of the novel coronavirus, it headed out to sea enforcing health and safety practices that will now become standard for the foreseeable future on U.S. Navy ships. And in an effort to keep a “COVID-free bubble” for its sailors at sea during the pandemic, the Navy will only allow ports of call at a select number of Navy bases around the world that will serve as “safe havens.”

“We remain focused on protecting our total workforce, it remains our top priority,” Vice Admiral Phillip Sawyer, Deputy Chief of Naval Operations for Operations, Plans, and Strategy, who is in charge of the Navy’s COVID-19 response, told reporters earlier this week. “We will continue to operate in what we call the new normal COVID environment.”

Many of the Navy’s health and safety practices to prevent the spread of the coronavirus were lessons learned from the mass outbreaks of the virus aboard the aircraft carrier USS Theodore Roosevelt and the USS Kidd, a guided-missile destroyer. Including regular testing, the wearing of masks and social distancing are practiced in all Navy units, but a main focus is on ships at sea where close quarters can facilitate a quick spread of the virus among the crew.

Now, before Navy ships head out on a deployment, crews are tested and quarantined so that no one will bring the virus aboard a ship. To ensure that the ships remain a “COVID-free bubble,” the Navy is now developing new rules for where its ships can make ports of call.

“Anytime that you’re going to allow a threat vector into your bubble, you have to be concerned,” Sawyer said. “Whether that’s logistics coming over from a tanker, a COD flight coming in, or a ship, going into a port. And so, we are developing those procedures in our ports, as we speak.” COD flights are the fixed wing aircraft that transport supplies and personnel aboard aircraft carriers.

The initial suspicion was that the crew of the Roosevelt became infected with the virus during a port of call in Vietnam in March, but Navy officials now believe the virus came aboard the ship via flight crews that arrived on the vessel.

Sawyer said that for now, the Naval base at Guam will be a “COVID-free bubble” for ships in the Pacific region so they can make a port of call and plans are in the works for the same at a base in the Middle East and another in the Mediterranean.

“We’ve got a couple of locations that we’ve identified that we’re doing the same on, so that we can pull in and get R&R for the crew, a chance to relax a little bit, get some burgers, swim in the water.”

While setting up the bubbles at U.S. Naval facilities is a challenge, Sawyer said an even bigger challenge would be enabling a port of call at a non-U.S. facility overseas.

“Areas under our control, the ability to create safe havens, certainly is the first step,” said Rear Adm. Bruce Gillingham, the Navy’s Surgeon General. “How we do that in cooperation with our host and partner nations I think, will then follow.”

Beyond the setup in Guam, a Navy spokesperson noted that the USS Blue Ridge, the command ship for the Navy’s Seventh Fleet, conducted a “safe haven” port of call at Okinawa two weeks ago.

Sawyer said the testing and social distancing requirements are not intended to be long-term changes, but they will remain in place until a vaccine is developed. However, he acknowledged that it is a prospect that may not be possible for a year to 18 months from now at the earliest.

For the rest of its deployment in the western Pacific, the crew of the Roosevelt will be required to wear masks at all times, maintain social distancing and constantly disinfect the ship.

The coronavirus outbreak on the carrier ultimately infected nearly a quarter of the 4,865 sailors on the ship, including one who died.

As the carrier left Guam on Thursday, 350 sailors remained behind, most of them still in isolation to recover from their illness and some of whom were left behind to provide them support and care.

Sailors who recover from the virus will be flown back to the carrier while it is in the area, but those who will need more time will be flown to their next assignment.