Lethal messenger

El Niño brings deadly disease to South America

Published: Thursday 28 February 2002

El Niño causes more than just physical destruction. It spreads diseases as well (Photo: Greenpeace)

WHAT does the temperature of the sea and deadly South American disease have to do with each other? A lot, say climatologists at the US national Aeronautical Space Administration (NASA) and the US military health specialists.

They have used changes in the sea surface temperature to predict outbreaks of Bartonellosis, an insect-borne highly fatal disease. The researchers, www.sciencedaily.com reported on January 21, have found that the worst outbreaks of the disease 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 NASA’s 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.

“It appears that the disease comes in weather-related cycles,” said Larry Laughlin, Chairman of the US 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 of the study were presented on January 17 at the American Meteorological Society Meeting in Orlando, Fla.

Earth scientists at NASA teamed up with Laughlin’s group at USUHS to study Bartonellosis which causes 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. “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 per cent of cases if left untreated, it is important to identify the factors behind 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 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 led 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. The study marks the first time that researchers from the two widely divergent disciplines of climatology and disease prevention have collaborated.

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