Malaria is thought to have been part-and-parcel of life in the East Anglian flatlands from the 15th century until about 100 years ago, when it died out as medical care improved and effective drugs became cheaper.

But some scientists fear the illness – once known as the "ague" or "marsh fever" – may reappear as global warming provides favourable conditions in which the parasites which cause it can thrive again.

Regional microbiologist for the Health Protection Agency in the East of England Dr Tim Wreghitt stressed there were no concerns over malaria becoming a large-scale menace once more.

But he said there could be "clusters" of infections if the warmer weather allows the parasite to multiply more quickly and be transmitted between people by the mosquitoes which carry it.

Dr Wreghitt said: "We are saying there may be clusters of cases, but it's unlikely to cause large outbreaks.

"There might be two or three cases following one case where someone has brought the disease in from abroad before the health service stamps on it."

Malaria – the word comes from the medieval Italian for "bad air" – may have been present in England since Roman times.

From the late middle ages it was common along the coasts and estuaries of south east and northern England, and in the Fens.

In a bid to ward off the disease, Fenland residents took opium extracted from locally-grown poppies, sometimes becoming addicts. They also supped opium-laced beer.

Malaria lingered into the 20th century, and after the First World War conditions were still so conducive to its spread that soldiers who had returned from Greece caused a mini epidemic, transmitting it to 500 civilians in Kent.

It is that sort of scenario which boffins fear could happen again as the climate changes.

Currently there are about 2,000 cases of malaria in this country a year among travellers who have returned home with the disease, leading to about 20 deaths.

But the boffins are worried global warming may allow the illness to spread from an infected person into the wider population.

Hotter weather speeds up the multiplication of the malaria-causing parasite inside the female Anopheles mosquitoes which carry it, increasing the chances of a bite from the insects transmitting the disease.

Dr Wreghitt said: "The higher temperatures mean that it takes a shorter amount of time for the malaria bugs to replicate inside the mosquito.

"There are parts of the country, like the Fens, where there are more of the mosquitoes, so that's where there might be a limited risk and small clusters of cases.

"It's not a very likely threat, but people are watching it. It's on the horizon and being kept under review."