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Disease Traced to Extreme Weather

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  • Mike Neuman
    http://www.latimes.com/news/science/la-sci- cholera4aug04,0,2423790.story?coll=la-home-science Disease Traced to Extreme Weather Study of cholera rates in
    Message 1 of 1 , Aug 5 2:10 PM

      Disease Traced to Extreme Weather
      Study of cholera rates in Bangladesh could link global warming to
      infectious outbreaks.
      By Charles Piller
      Times Staff Writer

      August 4, 2005

      An analysis of four decades of disease records from Bangladesh shows
      that periods of extreme rainfall, drought or high temperatures can
      sharply increase cholera rates, a pattern that some researchers
      believe bolsters claims that global warming will increase disease

      The effect of weather on disease can be dramatic. In one period of
      turbulent weather from 1992 to 1994, the study found a six- to eight-
      fold increase in the number of cholera cases.

      The study, published today in the journal Nature, found lesser
      increases during other periods of severe weather.

      The researchers found that both floods and droughts promote cholera

      Floods caused by heavy monsoons often contaminate drinking water.
      Droughts and heat waves, sometimes caused by warming waters in the
      nearby Bay of Bengal, promote growth of the cholera bacterium in
      ponds and rivers.

      Although the research does not directly address global warming, it is
      among the first to show that extreme weather can alter disease

      "What this shows is that meteorological factors are dominant," said
      Dr. Paul R. Epstein, associate director of the Center for Health and
      the Global Environment at Harvard Medical School. He was not involved
      in the study. "It's the extremes that are bad for our health."

      Scientists have long suspected that climate variability fosters the
      spread of infectious diseases such as cholera, malaria and dengue
      fever. But firm conclusions have proved elusive because other
      factors, particularly migration rates and immunity from past exposure
      and vaccination, also have large effects.

      In this case, complete demographic and disease records in Bangladesh
      helped investigators separate out those factors.

      Cholera, a major problem in developing nations, is caused by Vibrio
      cholerae, a bacterium that spreads through contaminated food and
      water. It causes severe diarrhea, and without rapid treatment often
      leads to dehydration and death.

      American, Spanish and Bangladeshi researchers studied the severity of
      cyclical cholera outbreaks in Matlab, Bangladesh, in the Ganges and
      Brahmaputra river deltas.

      They examined disease rates and climatic conditions, including
      rainfall, from 1966 to 2002. The severity of cholera outbreaks
      corresponded to harsh conditions stimulated by El Niño, a weather
      pattern with global effects that stems from warming in the Pacific

      "Even when you take the degree of immunity into account, there is
      still solid evidence for the role of climate variability in cholera
      rates," said Mercedes Pascual, an ecologist at the University of
      Michigan and coauthor of the study.

      Systems designed to track local immunity levels, and monitor ocean
      temperature and rainfall, could eventually predict cholera outbreaks
      a step that could help scientists determine effects of global
      warming on disease patterns, she said.
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