Afghan virus: 20 more cases

The source of the illness that has struck UK marines remains a mystery

BAGRAM, Afghanistan (CNN) -- Another 20 British soldiers in Afghanistan have displayed symptoms of a mysterious disease, Defence ministry officials said.

The total number of soldiers affected rose to 38 on Friday. One is seriously ill and is being flown back to Britain, officials said.

News of the new cases of the sickness came as a force of 1,000 mostly UK marines were engaged in a battle with suspected al Qaeda and Taliban fighters in the Afghan mountains. (Full story)

On Wednesday, 18 British medical personnel at a field hospital fell ill with symptoms including severe diarrhoea, vomiting and a high fever. At least eight were flown to Europe for treatment.

British officials discovered the possible new cases Thursday after a senior medical officer ordered a check of all British troops deployed at Bagram air base "in order to identify anyone who displayed the symptoms of diarrhoea and vomiting."

CNN.COM SPECIAL REPORT  CNN NewsPass Video  Agencies reportedly got hijack tips in 1998  MORE STORIES Intelligence intercept led to Buffalo suspects Report cites warnings before 9/11  EXTRA INFORMATION Timeline: Who Knew What and When? Interactive: Terror Investigation Terror Warnings System Most wanted terrorists What looks suspicious? In-Depth: America Remembers In-Depth: Terror on Tape In-Depth: How prepared is your city?  RESOURCES On the Scene: Barbara Starr: Al Qaeda hunt expands? On the Scene: Peter Bergen: Getting al Qaeda to talk

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

British officials have described the sickness as similar to a very severe form of gastroenteritis -- the irritation and inflammation of the digestive tract. All the sick personnel have been placed on antibiotics.

British Defence Minister Geoffrey 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 Defence said Wednesday. "It will be reopened for normal medical cover as soon as possible."

Some 334 British troops, most at 34 Field Hospital, have been put under quarantine.

Military officials have rejected the possibility of bio-terrorism.

About 5,000 soldiers from some 10 countries are in Bagram. None of the about 2,700 American troops deployed there are thought to have contracted the illness, U.S. military spokesman Maj. Bryan Hilferty said on Thursday.

British marines on patrol in Bagram

British Defence Minister Geoffrey Hoon told the House of Commons on Thursday that 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 stabilised and they were expected to improve.

Royal Marines spokesman Lieutenant Colonel Ben Curry said on Friday that the illness had "absolutely not" impaired British forces' operational capability.

He told the BBC: "Unfortunately, we have had some additional cases, one listed as very seriously ill.

"Two have been given some additional prophylactics and are responding well to that treatment.

"There are an additional 17 who have had a degree of diarrhoea and vomiting. That is an occupational hazard working out in these climes."

For many of those taken ill, the worst aspect of their condition was that they were missing out on participating in the action currently taking place against Taliban fighters in the south east of Afghanistan, he suggested.

"They are now recovered, fit and healthy and rather sad because they are sitting in their base and missing the show," he said.