The Pentagon said Wednesday a Marine based in Southern California has been confirmed to be ill with swine flu and is under quarantine, along with about 30 other Marines.

A Marine spokesman at the Pentagon, Maj. David Nevers, said the sick Marine was doing well and his condition continued to improve. Nevers said approximately 30 other Marines who had been in contact with the sick Marine at the Twentynine Palms base will be held in quarantine for five days as well as to see whether they show symptoms.

Officials earlier had said 37 Marines who had come into contact with the sick Marine were being restricted from going to the mess hall and troop formations. It wasn't immediately possible to reconcile the conflicting numbers.

The sick Marine's roommate also was in quarantine but was not showing any symptoms of swine flu.

The ill Marine suffered from vomiting and other flu-like symptoms, Gen. James Conway, the Marine Corps commandant, said at a Pentagon briefing before the Marine was confirmed with the flu.

But, he added, "He's doing fine. He's up and about, he says he feels pretty good. ... There appears to be no threat him in terms of loss of life."

The Pentagon would not identify the Marine.

His roommate and the other Marines were receiving Tamiflu, Conway said. But the ailing Marine was not because "Tamiflu would not help him at this point."

The Marine first complained of being sick on Saturday.

It's not clear how he may have contracted the virus. Conway said the Marine had not been to Mexico, but had traveled around the San Bernardino Valley area of Southern California.

Conway said no additional doctors or medications have been needed at the base so far. The military has 7 million doses of Tamiflu and other anti-viral treatments stockpiled for its troops.

"Our concern is the obvious exposure to other people and the potential spread," Conway said. "And I'm confident we have a very aggressive doctor out there that is going by the book and being a little aggressive even beyond that, in terms of making sure that Marines are not exposing themselves to other Marines."

As many as 15,000 Marines are usually stationed at Twentynine Palms, the Marine Corps' largest base. But many are currently deployed across the world, and Conway did not immediately know how many were on base now.

The Marine is the first possible case of the illness that has shown up in America's armed forces of some 1.4 million soldiers, sailors, airmen and Marines, Pentagon spokesman Bryan Whitman said.