The move comes as U.S. aircraft carriers suffered from outbreaks of the novel coronavirus disease that has already infected hundreds of sailors.

The People’s Liberation Army deployed Type 22 missile boats to the East Sea for four days of live-fire exercises late last month involving warfighting scenarios that an unnamed military expert told the ruling Chinese Communist Party’s Global Times newspaper on Thursday were designed to boost the vessels’ coast combat skills. Maneuvers also reportedly involved countermine, damage control and rescue operations.

The Type 22 fleet, dubbed “HOUBEI-class wave-piercing catamaran missile patrol boats” by the Pentagon, is designed to use stealth and speed to overcome much larger targets such as aircraft carriers, the premier symbol of U.S. power projection across the globe. In the Pacific, the U.S. has deployed aircraft carriers and advanced naval assets to challenge China’s vast territorial claims.

But at least four of the advanced warships have been linked to cases of COVID-19, the coronavirus disease first observed late last year in China but that is now reported in the U.S. more than any other country. One such ship, the Guam-anchored USS Theodore Roosevelt has registered some 416 cases as of Thursday, including one sailor who had to be rushed to the hospital after he was found unconscious aboard the hard-hit vessel.

The carrier’s former commanding officer, Captain Brett Crozier, also reportedly tested positive for COVID-19 after he was removed from his post last week over a leaked memo appealing to his superiors for support in quarantining personnel. In a speech on board the USS Theodore Roosevelt, former Acting Navy Chief Thomas Modly accused Crozier of either betraying the armed forces or being “too naive or too stupid” to lead the ship. He was forced to apologize and eventually resigned Wednesday after his remarks were leaked to the media.

Elsewhere in the Pacific, the U.S. Navy has reported COVID-19 cases among sailors stationed on the USS Ronald Reagan currently in Yokosuka, Japan and, on the other side of the world’s largest ocean, at least one service member assigned to the Pudget Sound, Washington-based USS Carl Vinson has also reportedly tested positive for the disease. The USS Nimitz, readying to deploy from further down the U.S. coast in San Diego, California, was revealed Thursday to have “a very small number of breakouts,” according to Air Force General John Hyten, vice chairman of the Joint Chiefs of Staff.

“It’s not a good idea to think that the Teddy Roosevelt is a one-of-a-kind issue,” Hyten told reporters at a press briefing Thursday. “We have too many ships at sea, we have too many deployed capabilities. There’s 5,000 sailors on a nuclear-powered aircraft carrier. To think that it will never happen again is not a good way to plan.”

“Our military remains ready and continues to operate around the globe,” he added.

Navy Lieutenant Commander Megan Isaac offered Newsweek further details on the situation aboard the USS Nimitz.

“A sailor displayed symptoms, was placed into isolation off the ship out of an abundance of caution, and subsequently had testing that was inconclusive. Sailors that had been in close contact with the individual were also removed from the ship as a precaution and placed into quarantine. That sailor remains off the ship,” Isaac said.

“Regarding the second Nimitz sailor that has been reported as positive for COVID-19, they tested positive while out of the state on leave in early March. That sailor remains in that location and has not been to or aboard Nimitz since departing the area on leave,” she added.

As for the question of U.S. military posture amid the pandemic, she said “our ships and carriers continue to serve and deploy around the world, ready to execute missions across the full spectrum of fleet operations to safeguard U.S. national interests and those of our allies, even in this crisis.”

“The Navy protects its people and our people protect the nation,” she added. “The Navy is implementing safety mitigations to maintain the health and wellbeing of our Sailors and their families at units and installations around the globe.”

The U.S. armed forces have increasingly shifted focus in recent years from warzones across the Middle East and Afghanistan to East Asia, where top economic competitor China has expanded its military, economic and political influence. The command known to the U.S. and its allies as the Indo-Pacific has witnessed increased confrontation between the conflicting interests of Washington and Beijing.

As the COVID-19 crisis spread throughout the ranks of the U.S. Navy, Arleigh Burke-class destroyer USS McCampell transited the Taiwan Strait, a stretch of sea claimed by both China and self-ruling Taiwan, which Beijing also considers under mainland sovereignty. The journey followed similar trips by Ticonderoga-class guided-missile cruisers USS Chancellorsville in February and USS Shiloh in January.

Chinese Defense Ministry spokesperson Senior Colonel Ren Guoqiang condemned what he called “provocative actions” by the Pentagon shortly after the latest U.S. Navy crossing of the disputed waters. “We will absolutely not allow any foreign forces to play the Taiwan card, and will not tolerate any attempts of secession. The PLA has the will, confidence and capability to thwart all secession efforts and safeguard the nation’s sovereignty and territorial integrity,” he added.

Around this same time, Chinese guided-missile frigates Xuchang and Yulin conducted live-fire operations, including anti-submarine training in the South China Sea.

China has two aircraft carriers of its own, compared with 20 operated by the United States. Chinese President Xi Jinping has sought to expand his country’s naval forces, which were reportedly set to be bolstered in the coming years by at least two more aircraft carriers currently in the works.

While Xi mobilized significant military resources to battle the COVID-19 outbreak that first emerged in Wuhan, the country has ceased reporting new instances of the coronavirus disease and the central city once the epicenter of the disease lifted its 76-day lockdown on Wednesday. Now, the U.S. finds itself devoting substantial armed forces assets of its own to battle the growing coronavirus crisis, something the CIA warned in a memo late last month could benefit China and Russia’s long-term efforts to elevate their status on the world stage, as Newsweek previously reported.

Moscow and Beijing have called on Washington to cooperate in battling the pandemic while U.S. and China spar over the origin of the virus.

In response to Secretary of State Mike Pompeo’s allegations Wednesday that the “information didn’t flow fast enough” in the early days of the epidemic, Chinese Foreign Ministry spokesperson Zhao Lijian defended his country’s handling of the crisis, telling reporters Thursday: “We hope that the American people can also overcome the epidemic at an early date and resist the narrow-minded approach of certain politicians who politicize the epidemic and stigmatize China to shift the blame.”

The above graphics were provided by Statista.

This story has been updated to include a statement from a representative of the Navy Office of Information.