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The Navy says an outbreak of coronavirus aboard an aircraft carrier in the Pacific has forced it to divert to Guam, where all 5,000 aboard will undergo testing.

The USS Theodore Roosevelt remains "operationally capable," according to the acting secretary of the Navy, Thomas Modly.

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"Sailors flown off the ship are doing fine, none required hospitalization — mild aches and pains, sore throats," Modly said Thursday at a Pentagon press briefing, adding they were "in quarantine now on Guam."

Other officials said the number of infected sailors has risen sharply — from initial reports of three to "dozens" as of Thursday.

"Our medical team aboard USS Theodore Roosevelt is performing testing for the crew consistent with CDC guidelines, and we are working to increase the rate of testing as much as possible," said the Chief of Naval Operations, Adm. Mike Gilday.

Priority will be given to those showing symptoms or who had been in close contact with sailors who have tested positive already, as well as to essential crew members. Those who test positive will be isolated, Gilday said.

No sailors have been hospitalized or are seriously ill, according to Gilday. Deep cleaning of the ship is ongoing.

"We're taking this day by day," Gilday said. "Our top two priorities are taking care of our people and maintaining mission readiness. Both of those go hand in glove."

The carrier is the first U.S. Navy ship to have a reported an outbreak while at sea. About 800 test kits are aboard and more were being delivered, Modly said.