WASHINGTON (Reuters) - The U.S. military’s official tally of servicemembers and related personnel who have been infected by the coronavirus likely undercounts the actual total, the Pentagon acknowledged on Tuesday, as a second servicemember in the United States tested positive for the virus.

The disclosure is another example of the risk to the U.S. military even as it tries to limit the fallout from the global spread of the virus on the more than a million active-duty troops around the world -- including in places like Italy and South Korea, which have experienced major outbreaks.

Officials, speaking on condition of anonymity, say the generally low age and good health of U.S. troops is a mixed blessing of sorts -- allowing U.S. servicemembers to better withstand the virus, but perhaps also allowing them to become carriers who fail to exhibit the kinds of symptoms that trigger testing.

“I think that it is likely, given what we are seeing around the world, and the fact that we have people all over the world, that there are more,” Joint Staff Surgeon Air Force Brigadier General Paul Friedrichs told a Pentagon news briefing.

Joint Base Lewis-McChord in the U.S. state of Washington said a servicemember and spouse had got the coronavirus and were being quarantined at their off-base residence. Twelve people who had contact with them were also placed in quarantine.

The case at Lewis-McChord would be the fourth U.S. servicemember globally infected and the second in the United States, after a Marine in the Washington, D.C., area was reported to test positive over the weekend.

He worked at the Defense Security Cooperation Agency, which is located just blocks from the Pentagon and helps oversee foreign military sales and international military educational partnerships. The Marine had returned last month from Ethiopia.

The Marine is being treated at Fort Belvoir hospital and is doing well, the Pentagon said.

Beyond the servicemembers there are also six Pentagon personnel confirmed with the virus: one civil servant, four dependents and one contractor, the Pentagon said.

There were also as many as six presumptive positive cases, possibly including at least one of the two at Lewis-McChord, it said.The Army disclosed on Monday that the top U.S. Army commander in Europe may have been exposed to the coronavirus during a conference with land force commanders in Europe on Friday in Wiesbaden, Germany.

In a photo here, Lieutenant General Christopher Cavoli is pictured sitting next to an unnamed Italian military officer whose face cannot be seen in a military photo of the event. Reuters reported on Sunday that Italian army Chief of Staff General Salvatore Farina contracted the virus.

Defense Secretary Mark Esper postponed an upcoming trip to India, Uzbekistan and Pakistan over the coronavirus, in part out of concerns that someone in his delegation might have to be quarantined overseas if they developed concerning symptoms.