The mystery illness that has struck British troops serving in Afghanistan is believed to be the so-called "winter vomiting bug".
Several positive diagnoses of the disease, also known as Norwalk-like virus, have been made, and although tests are not complete on all those affected it is "highly likely" it is to blame.
The strain is "virtually identical" to the bug which swept Britain earlier this year, a source says.
The harsh conditions faced by troops in Afghanistan, particularly dehydration caused by the heat, produced more extreme symptoms than the disease has in the UK, confusing experts, the source adds.
However there is "no suggestion" the British forces had taken the disease with them to the Royal Marines' Bagram airbase.
The disease is thought to have hit 25 UK troops, with others presenting milder symptoms, who are thought to be suffering from more common diarrhoea bugs.
PA