TROPICAL DISEASES SPREADING NORTH Warning as mayor orders spraying of New York
Paul Brown, Environment Correspondent Saturday September 11, 1999
Leading experts on climate change warned last night that global warming is making cities in the northern hemisphere more vulnerable to outbreaks of potentially lethal strains of tropical diseases.
The warning came as the mayor of New York, Rudolph Giuliani ordered the spraying of the entire city with insecticide from helicopters in an attempt to eradicate mosquitoes which are spreading the brain disease encephalitis. So far there have been three deaths and nine other confirmed cases. A further 60 suspected cases have been identified.
Unstable weather in North America and Europe is allowing pests and diseases to migrate north, according to Paul R Epstein, an associate director of the Centre for Health and the Global Environment at Harvard medical school. "We must all prepare for such nasty surprises," he said.
Doctors in southern England have already been warned by the department of health to look out for malaria cases caused by locally-bred mosquitoes.
Dr Epstein said the extreme weather events - droughts followed by tropical downpours - suffered by New York this summer were providing ideal breeding conditions for mosquitoes, particularly those which carry tropical diseases, as there were few natural predators to feed on larvae.
He said that New York had also suffered two cases of locally-transmitted malaria in the last few weeks - another sign that climate change was allowing the survival of tropical diseases in an area which had always been considered too cold.
It is New York's first confirmed outbreak of St. Louis strain encephalitis, which is fatal in 10% of cases. Spraying is aimed at the stagnant pools where the larvae thrive and is likely to continue until frosts kill off the mosquitoes.
"This is scaring the hell out of the people of New York," Dr Epstein said. "The psychological cost and the costs of spraying are probably greater than the direct medical bills, but they show the kind of costs associated with an unstable climate, and the extreme weather associated with it.
"Washington has been suffering a severe drought and is now being hit by thunderstorms - it's the same pattern. Perhaps they will finally get the message that it is time to do something about climate change."
The World Heath Organisation in Geneva has a unit which is monitoring the spread north of malaria and other tropical diseases.
Dr David Viner, a senior scientist at the climatic research unit at the University of East Anglia has written a report on the expected return of malaria to Southern Spain. He said: "The malaria-carrying mosquitoes die off if it's too hot or it's too cold, so with climate change they are gradually moving north as temperatures warm up. Malaria is the biggest killer on the planet which is why everyone is so worried about it.
"Just to give you some idea they are spending $100m [£61.6m] a year in Florida to try and eradicate malaria. It is only a matter of time before the climate envelope in which it and other tropical diseases survive moves northwards both in Europe and the US."
He said that malaria had been prevalent in East Anglia during the middle ages when Britain was warmer and it could return. Department of environment scientists said last year that conditions in Britain were already suitable for malaria mosquitoes to survive.
According to Dr Epstein, New York's warmer winters were already allowing some encephalitis-carrying mosquitoes to survive although the cold still killed off malaria mosquitoes.
"In general, climate constrains the range of most infectious diseases, while weather affects the timing and intensity of outbreaks," he said.
"Recent weather-related disasters like Hurricane Mitch have spawned clusters of water, rodent and mosquito-borne infections. They were spreading diseases further north than previous seen."
The march north of the Saint Louis strain of encephalitis was recorded in predictions made by the UN's intergovernmental panel on climate change in 1998. Its report suggested that outbreaks along the east coast, south of New York, were associated with warm winters and hot dry summers.
In the European chapter of the report, it predicted that warmer conditions for vector organisms - such as ticks, mosquitoes and sand flies - that spread warm climate diseases increase the potential for outbreaks in Europe.
Increased tourism is also playing a part. About 2,000 cases of "airport" malaria - in which the disease is carried back to Britain by tourists - were diagnosed in England in 1990 and there are usually 10-12 fatalities each year.
These cases could lead to local populations of mosquitoes becoming infected with the parasite. "It is important to strengthen current policies of surveillance," the report says.