Guardian (London) - September 11, 1999
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.