Health: Warmer weather brings threat of malaria and cholera to Britain

Global warming could bring olive trees to southern Britain as the world's climate changes more rapidly in the next 100 years than in the previous 10,000. But the rise in temperature could also lead to outbreaks of tropical diseases such as cholera and malaria. Jeremy Laurance, Health Editor, anticipates the hidden dangers of warmer days.

Rising temperatures across the world will spread tropical illnesses to Europe and North America and change the global pattern of disease, scientists predict.

Malaria, cholera, tick-borne fevers and respiratory illnesses are all expected to grow as a result of the accumulation of carbon dioxide, methane and other gases in the atmosphere which is believed to be causing global warming.

While warmer temperatures may be welcomed by wine producers and olive growers hoping to extend their operations to northern Europe, the spread of diseases could bring misery to many.

Specialists at the London School of Hygiene and Tropical Medicine and the Royal Free Hospital School of Medicine have estimated the likely health effects of the 1-3.5 degrees centigrade rise in global temperatures forecast by the Intergovernmental Panel on Climate Change, a United Nations scientific body set up to advise governments worldwide.

Writing in the British Medical Journal, Professors Tony McMichael and Andrew Haines say storms, floods and heatwaves are likely to increase. Air pollution is likely to worsen, especially summer smogs which are sensitive to a variation in temperatures.

Diseases likely to become more common in Europe include malaria, which was widespread in Britain until improved public health measures eliminated it in the early part of this century. Viral encephalitis, a swelling of the brain spread by ticks, and Lyme disease, also spread by ticks and causing arthritis and skin rashes, are expected to grow. Leishmaniasis, a disease affecting the liver and spleen and causing fever and death if untreated, which is found in the eastern Mediterranean, is also predicted to spread northwards. It is carried by the sandfly.

Professor McMichael said yesterday that cases of local transmission of malaria in New York and Europe had increased in the last decade. "It is difficult to say whether the malarial mosquito will come over the horizon in Britain. What we can say is that climate change will make it easier for this disease to spread."

Cholera broke out in Peru, South America, in 1991 for the first time for 100 years. US scientists believe warming of the coastal waters and increased dumping of phosphate and nitrate wastes stimulated the growth of algae which acted as a natural host for the cholera bacteria.

Professor McMichael said the same algae were common in the Mediterranean. "If there were sufficient shifts in the temperature of coastal waters in Britain it could be a problem here too," he said. Individuals and society had to tackle the problem of global warming by reducing production of carbon dioxide, he warned.