Global Warming and West Nile Virus

[Louis Proyect <lnp3@xxxxxxxxxxxxx>]

New York Times, July 24, 2000

Giuliani Says Aerial Spraying Will Be Added to the War Against the West
Nile Virus

By ERIC LIPTON

New York City's war on the West Nile virus is intensifying, with Mayor
Rudolph W. Giuliani announcing yesterday that the city planned to add
helicopters to its arsenal of mosquito-killing tools and would expand its
ground-based pesticide campaign to include parts of Brooklyn as well as
Staten Island and Queens.

The escalating effort in New York City echoes steps being taken by local
and state governments throughout the New York area.

The virus, which killed 7 people and seriously sickened 55 others last
year, has not been detected in people this year. But at least 40 infected
birds and 3 pools of infected mosquitoes have been found in New York City
and 8 neighboring counties in New York, New Jersey and Connecticut, the
authorities said. At the end of last month, the virus had been confirmed in
only a few birds in Bergen County, N.J., and Rockland County, N.Y.

Full article at:
http://www.nytimes.com/yr/mo/day/news/national/regional/ny-bug.html

=====

>From "Is Global Warming Harmful to Health?" by Paul Epstein, in the current
Scientific American (www.sciam.com):

The increased climate variability accompanying warming will probably be
more important than the rising heat itself in fueling unwelcome outbreaks
of certain vector-borne illnesses. For instance, warm winters followed by
hot, dry summers (a pattern that could become all too familiar as the
atmosphere heats up) favor the transmission of St. Louis encephalitis and
other infections that cycle among birds, urban mosquitoes and humans.

This sequence seems to have abetted the surprise emergence of the West Nile
virus in New York City last year. No one knows how this virus found its way
into the U.S. But one reasonable explanation for its persistence and
amplification here centers on the weather's effects on Culex pipiens
mosquitoes, which accounted for the bulk of the transmission. These urban
dwellers typically lay their eggs in damp basements, gutters, sewers and
polluted pools of water.

The interaction between the weather, the mosquitoes and the virus probably
went something like this: The mild winter of 1998-99 enabled many of the
mosquitoes to survive into the spring, which arrived early. Drought in
spring and summer concentrated nourishing organic matter in their breeding
areas and simultaneously killed off mosquito predators, such as lacewings
and ladybugs, that would otherwise have helped limit mosquito populations.
Drought would also have led birds to congregate more, as they shared fewer
and smaller watering holes, many of which were frequented, naturally, by
mosquitoes.

Once mosquitoes acquired the virus, the heat wave that accompanied the
drought would speed up viral maturation inside the insects. Consequently,
as infected mosquitoes sought blood meals, they could spread the virus to
birds at a rapid clip. As bird after bird became infected, so did more
mosquitoes, which ultimately fanned out to infect human beings. Torrential
rains toward the end of August provided new puddles for the breeding of C.
pipiens and other mosquitoes, unleashing an added crop of potential virus
carriers.

(Paul Epstein, an M.D. trained in tropical public health, is associate
director of the Center for Health and the Global Environment at Harvard
Medical School. He has served in medical, teaching and research capacities
in Africa, Asia and Latin America and has worked with the Intergovernmental
Panel on Climate Change, the National Oceanic and Atmospheric
Administration, and the National Aeronautics and Space Administration to
assess the health effects of climate change and to develop health
applications for climate forecasting and remote-sensing technologies.)

Louis Proyect

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