LANDSTUHL, Germany — Four servicemembers suspected of having the H1N1 virus, or swine flu, have tested positive for the illness, Europe Regional Medical Command officials said Wednesday.

The four have already been isolated at Landstuhl with two other servicemembers who have swine flu, said Steve Davis, a spokesman for ERMC.

The previous two confirmed cases are a soldier from Mannheim, Germany, and a soldier from Stuttgart, Germany. They were also the first servicemembers in Europe diagnosed with the illness. At least one of them started showing symptoms of H1N1 on May 27.

The others ERMC confirmed as having the virus are two sailors from Naples, Italy; an airman from Spangdahlem Air Base, Germany; and an airman from Incirlik Air Base, Turkey. They are being treated with the antiviral flu medication Tamiflu and are responding well, Davis said.

ERMC and the U.S. Army Center for Health Promotion and Preventive Medicine have worked with the servicemembers’ home bases to interview anyone who might have come into contact with them to determine if more people might have been infected, medical officials said in a release.

“There is no cause for undue concern in the communities [those servicemembers came from]. There are no signs of other cases that we are aware of in the military community,” Davis said. “It is still unclear how it was spread amongst them.”

ERMC officials said they are also prepared if the World Health Organization declares an H1N1 pandemic, as some media outlets have reported the agency is preparing to do. According to the WHO, 25,288 cases of swine flu and 139 deaths from the sickness had been reported worldwide as of Monday.

“We have pandemic plans in place. These plans are very extensive and they have been in place for quite some time,” Davis said.