The symptoms appear suddenly with a headache, high fever, abdominal and joint pain, and vomiting. As the illness progresses, patients can develop large areas of bruising and uncontrolled bleeding. In at least 30 percent of cases, Crimean-Congo viral haemorrhagic fever is fatal.

This month a 38-year-old garage owner from Glasgow, who had been to his brother’s wedding in Afghanistan, became the UK’s first confirmed victim of the tick-borne viral illness when he died at the infectious disease unit at London’s Royal Free Hospital.

It is a disease widespread in domestic and wild animals in Africa and Asia – and one that has jumped the species barrier to infect humans with deadly effect.

The unnamed man’s death was not the only time a foreign virus had recently struck in Britain for the first time.

Last month, a 49-year-old man entered a London hospital with a raging fever, severe cough and difficulty in breathing.

He bore all the hallmarks of the deadly severe acute respiratory syndrome (Sars) virus that killed nearly 1 000 people in 2003, but blood tests quickly showed this terrifyingly virulent infection was not Sars. Nor was it any other virus yet known to medical science.

Worse still, the gasping, sweating patient was rapidly succumbing to kidney failure, a potentially lethal complication that had not been seen before in such a case.

As medical staff quarantined their critically ill patient, fearful questions began to mount. The stricken man had recently come from Qatar in the Middle East. What had he picked up there? Had he already infected others?

Using the latest hi-tech gene-scanning technique, scientists at the Health Protection Agency started to piece together clues from tissue samples taken from the Qatari patient, who was hooked up to a life-support machine.

The results were extraordinary. The virus was from the same family as Sars, but its make-up was completely new. It had come