STUDY
LINKS EL NINO TO DEADLY SOUTH AMERICAN DISEASE
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In
a groundbreaking collaborative study, NASA climatologists and U.S. military health
specialists may have discovered a way to predict outbreaks of a deadly South American
disease by observing sea surface temperature. The
researchers found that the worst outbreaks of Bartonellosis, an insect-borne disease
highly fatal to humans, are closely related to the climate event El Niño.
These outbreaks occur one to three months after the warming of the tropical eastern
Pacific Ocean that is associated with El Niño. If confirmed, the findings
could enable health workers to stave off future epidemics before they begin. "We
now have strong evidence that there is a relationship between climate and Bartonellosis,"
said William K. Lau, head of the Climate Radiation Branch at the NASA/Goddard
Space Flight Center. "It's not proven yet, but we are
now one step closer." The
evidence could allow health officials to predict and combat epidemics far more
effectively.
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2 | | "It
appears that the disease comes in weather-related cycles," said Larry Laughlin,
Chairman of the Department of Preventive Medicine at the Uniformed Services University
of Health Sciences (USUHS). "If we can prove it, local health officials will
be able to take preventive action when they know a 'bad year' is coming. This
is a critical factor in developing countries where healthcare resources are limited."
The
findings will be presented on January 17 at the American Meteorological Society
Meeting in Orlando, Fla. NASA
earth scientists teamed with Laughlin's group at USUHS to study Bartonellosis,
a disease that is characterized by life-threatening anemia. There is also a chronic
form of the disease that manifests itself in blood-filled, wart-like skin lesions.
Bartonellosis appears to be spreading from the mountain valleys of Peru into other
regions of Andean South America.
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3 | | "We
think the disease is transmitted to humans by the bite of sand flies, much as
malaria is by mosquitoes," Laughlin said. "Since the acute disease is
fatal in 40 percent of cases if left untreated, it is important to identify the
factors that encourage its spread." The
group studied two regions of Peru known as Caraz and Cusco. While the mountainous
region of Caraz has a long history of Bartonellosis outbreaks, it was unknown
in the more southern Cusco until recently. The deadliest recent outbreak was during
the South American summer and fall months of December 1997 to May 1998. Since
the 1997-98 season was also the strongest El Niño event of the 20th century,
the scientists compared sand fly breeding observations with weather data from
NASA's Tropical Rainfall Measuring Mission (TRMM) satellite.
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4 | | "We
noticed that extremely high numbers of sand flies were collected during the 1997-98
season," Lau said. "That season had double the average number of Bartonellosis
cases. The disease also spread to the southern part of the country, where it had
not been seen before. The data lead us to believe that El Niño was the
dominant factor in the epidemic." Since
indications of El Niño can be seen by satellites months before it affects
the sand fly breeding season in South America, the scientists believe they can
serve as an advance warning of an approaching epidemic year. But further study
is necessary to strengthen the connection's validity.
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5 | | "We
were only able to use data between 1994 and 1999," Lau said. "There
was only one El Niño event during that period, and that's not enough to
establish a conclusive link. But we now think that, with further study, predictions
of epidemics will be possible in the future." The
study marks the first time that researchers from the two widely divergent disciplines
of climatology and disease prevention have collaborated. "This
is a prime example of how two organizations came together and did something that
wouldn't have been possible otherwise," Laughlin said. "Had we each
been left to our own devices, NASA might still be focusing on predicting El Niño
but not paying attention to disease, while we might be spraying the same amount
of insecticide every year with poor effect on disease control. As a result of
looking outside our own disciplines, though, we can now help more people while
saving money and effort." This
research is supported by NASA's Earth Observing System/ Interdisciplinary Science
investigation on hydrological processes and climate, and the Global Modeling and
Analysis Program of NASA, Earth Science Enterprise and a NOAA grant. NOTE:
This presentation, Session 6.6, will be given at the 82nd Annual meeting of the
American Meteorological Society, at the Orange County Convention Center on Thursday,
January 17 at 9:30am. Back
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