Study links El Nino and climate warming to diarrhea increase
February 3, 2000
Web posted at: 3:53 PM EST (2053 GMT)
LONDON (AP) -- After linking El Nino with illnesses such as malaria, cholera and dengue fever, scientists now have connected the climatic phenomenon with an increase in childhood diarrhea.
The research led by the Johns Hopkins School of Public Health also suggests for the first time that gradual temperature increases related to global warming could foster outbreaks of diarrhea in children living in developing nations.
Diarrhea kills as many as 3 million children under the age of 5 worldwide every year and sickens millions more, mostly in developing countries.
It normally is more prevalent during the warmer seasons but, until now, experts didn't know whether a change in temperature could play a role.
The study of 57,331 children in Lima, Peru, found that an increase in diarrhea cases between 1993 and 1997 was linked to even small rises in temperature, regardless of whether it was summer or
winter. In fact, the effect was greater in winter, even though the weather was cooler.
Overall, the study, published this week in The Lancet medical journal, found that for every 1 degree centigrade (1.8 degrees Fahrenheit) hotter than normal it became, 8 percent more children arrived at a local clinic for treatment of diarrhea.
The findings were similar for the 1997-1998 El Nino period.
The number of children brought to the clinic each day that winter was double what would have been expected for that time of year had El Nino not occurred, the study found.
El Nino, which involves the equatorial waters in the Pacific warming up, creating unusual weather patterns around the world, increased winter temperatures in Lima by about 4 degrees centigrade (about 7 degrees Fahrenheit).
A similar increase in temperatures brought on by El Nino in the summer was still connected to more diarrhea than usual, but the effect was not as strong, accounting for only a 50 percent rise in diarrhea cases, the researchers found.
"The potential effect of global warming on disease is controversial," said William Checkley of Baltimore-based Johns Hopkins, who led the study. "This study suggests there may be something to it for diarrhea."
It's plausible the researchers' findings could apply in countries other than Peru, said Dr. Tony McMichael, an epidemiology professor at the London School of Hygiene and Tropical Medicine who studies the effects of climate on disease.
"In general, a large proportion of infectious disease agents are very sensitive to slight changes in climate," said McMichael, who was not involved in the research. "This would give us a reasonable indication of how diarrhea agents react to changes in temperature in general, whether in water or in food."
Checkley said the stronger effect in winter could be due to the fact that the types of diarrhea common in winter and summer are different.
In hot weather, diarrhea caused by bacteria or parasites is more likely. Cooler temperatures appear to enhance the transmission of viral diarrhea, he said.
When the winters are hotter than normal, it could be that children are exposed to more sources of diarrhea, including the bacterial and parasite sort. El Nino also may prompt diarrhea-promoting behavior more common in the summer, such as more demand for water, the study said.
Dr. Olivier Fontaine, a diarrhea expert at the World Health Organization, said the observed link makes sense.
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