Speculation over mystery illness

Soldiers have reported fever, diarrhoea and vomiting.

As officials attempt to identify the mystery illness which has struck down 18 army personnel, and left around 350 soldiers at a medical hospital in Bagram under quarantine, BBC News Online examines what the illness might be.

The illness which has hit the British soldiers in Afghanistan has still not been officially identified, but experts believe it could be gastroenteritis, a serious stomach bug.

Dr Mahmoud Halablab, a microbiologist from King's College, London, said gastroenteritis, which causes stomach pain, vomiting and diarrhoea was the most likely reason for the soldiers' illnesses.

The viral infection is usually linked to unclean water or food, and is highly contagious.

It could be something specific to that area, maybe an unusual form of gastroenteritis

Dr Mahmoud Halablab, King's College, London

Dr Halablab said the apparently short incubation period of the illness matched how gastroenteritis progressed.

He said: "I'm really surprised that they don't already know what it is, unless it is some exotic virus, or an unusual type of a known virus.

"It could be something specific to that area, maybe an unusual form of gastroenteritis, which local people would be immune to, because they would have built up an immunity to it, but which could cause these serious symptoms in people new to the area."

Dr Halablab said doctors may be finding it difficult to confirm the condition because it can only be diagnosed by blood tests.

He added this might explain why the illness has not yet been identified.

It could also be a local version of the virus which Western doctors had not previously seen, he said.

That might also explain why some of the British troops are so severely affected.

Food link

Dr Paul Clarke, a former military medical consultant told the BBC: "I think it's true to say this is most likely to be a virus infection.

Dr Paul Clarke links the outbreak to food or water

"This, after all, is very common in travellers wherever you go and in particular where you've had a country ravaged by war, and poor sewage and other public health measures.

"I understand people may even have had access to local food.

"So I would think this is almost certainly a severe viral infection."

Dr Clarke, an expert in infectious diseases who now runs an advice clinic for travellers, said military campaigns had always been plagued by illnesses and soldiers do what they can to avoid them.

He said, although a biological attack would have been a concern in the Afghanistan outbreak, it would have been dismissed early on because the symptoms did not match.

Dr Clarke added: "The options, possibly of something like a typhoid organism, or a funny listeria organism being introduced into food is a possibility, but why go for the medical department?"

He said soldiers would be immunised against diseases such as typhoid, but added: "There are some things you can't immunise against.

"If you pick these things up in water or food, it's very difficult to legislate for that."

Fever

There have also been suggestions that the soldiers could be suffering from enteric fever.

It is a bacterial infection which has a slow onset with fevers, headaches and generally not feeling very well.

It is spread by food and water contaminated by faeces or urine from a carrier.

Salads can also be contaminated through infected water.

Diarrhoea or constipation can also be symptoms.

Effective antibiotic treatment is available, and with prompt treatment, severe complications are rare.

Symptoms

All the sick are military medical personnel working at 34 Field Hospital in Bagram which has now been closed - except to treat the fever.

The MoD has "categorically" confirmed the illness is not the result of a bio-terrorist attack.

There were fears when the first cases appeared that the soldiers could be suffering from meningitis but tests have ruled that "unlikely".

Soldiers first started reporting symptoms three days ago, including fever, diarrhoea and vomiting.

Tests on those affected are expected to identify the cause of this outbreak.