Updated

More than 400 sailors and three dozen civilians were being tested for tuberculosis after a sailor aboard the USS Ronald Reagan was diagnosed with the infectious disease.

Navy officials said Tuesday that the 32-year-old sailor was hospitalized last week with active tuberculosis and had been aboard the aircraft carrier when it returned July 6 after a six-month deployment.

During the final phase of the ship's return, about 1,200 friends and family joined the 4,800 sailors in Hawaii and continued the journey to San Diego.

Sailors and civilians who shared sleeping quarters with the infected sailor were being tested. After that, a decision will be made about whether to require additional testing, Capt. Frank Chapman said.

The sailor was initially placed in the isolation ward at San Diego Naval Medical Center. He has since returned to his home but remains in an informal quarantine while tests are being conducted, Chapman said.

"We're treating it as if he's very infectious," Chapman said.