Troops with mystery flu improving

British marines are on active duty in Afghanistan

LONDON, England (CNN) -- British troops stricken with a mystery illness at Bagram Air Base in Afghanistan are stable or improving, but medical officials still have not identified the illness or its cause.

British Defense Minister Geoffrey Hoon told the House of Commons on Thursday that there had been no new cases of the flu-like illness in the last 22 hours.

Hoon said three soldiers were in serious condition -- one who had been flown back to Britain, one at a U.S. hospital in Germany, and a third who remained at the British hospital in Bagram.

He said the conditions of all three had stabilized and they were expected to improve.

On Thursday, officials said the third soldier in serious condition and five other British medical personnel would be evacuated to Britain.

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Military officials quarantined about 300 people in a Bagram field hospital after 18 British medical personnel fell ill.

"The exact nature of the illness is not yet known and medical tests continue to isolate the cause," the British Ministry of Defense said earlier.

The first case appeared three days ago when one of the medical personnel came down with severe diarrhoea, vomiting and a high fever.

All the sick personnel have been placed on antibiotics.

Hoon said that the delivery of fresh rations had been halted and British forces were eating pre-packaged food.

"The illness appears to be contagious, and as a precaution 34 Field Hospital has been closed to all but similar cases," the Ministry of Defense said Wednesday. "It will be reopened for normal medical cover as soon as possible."

Until then, British troops will be treated at a German hospital in Kabul. Britain has some 1,700 Royal Marines in Afghanistan.

Meanwhile, U.S. military officials said one U.S. military person in Afghanistan has fallen ill and is to be airlifted to Uzbekistan. The officials said they have no idea if the case is related to the sick British troops.

In addition, the U.S. officials said one U.N. staff member in Kabul fell ill with typhoid fever and is being taken out of the country for treatment. That case is believed unrelated to the others.

-- CNN Producer Maria Fleet, CNN's Avril Stephens and Correspondent Barbara Starr contributed to this report.