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 Nio event of the 20th century, the scientists compared sand fly breeding observations with weather data from NASA's Tropical Rainfall Measuring Mission (TRMM) satellite.
"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 Nio was the dominant factor in the epidemic."
Since indications of El Nio 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.
"We were only able to use data between 1994 and 1999," Lau said. "There was only one El Nio 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
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Contact: Cynthia M. O'Carroll
cocarrol@pop100.gsfc.nasa.gov
301-614-5563
NASA/Goddard Space Flight Center
17-Jan-2002