Aedes aegypti has expanded its range in recent years to reinfest many parts of the Americas, areas where it was thought to have been eradicated by intensive post-World War II mosquito control programs. Its range includes the southern United States, mostly in the southeast and southern Texas.

But could the mosquito's range and populations change even more in response to large climate events like El Nino? According to Hopp, it probably has.

"Because El Nino events result in some regions being warmer and wetter, it's reasonable to believe that mosquito populations will be affected," she said. "This year, regions of South America, Southeast Asia and the Western Pacific had very large numbers of dengue cases compared to previous years, likely as a result of our recent El Nino."

Hopp's model depicts the worldwide population dynamics of the Aedes aegypti mosquito based on climatic variables, looking at the development at each life stage of the mosquito all over the globe.

Because the habits and preferences of Aedes aegypti are well known, Hopp is confident that it is possible to predict new areas where the mosquito could survive should it be introduced.

"In addition to modeling where the mosquito occurs, we model when the mosquito populations will be peaking during the year, and how large the population is compared to previous months and years," Hopp said. "Potentially, with the use of long-lead climate forecasts, we may model future populations and potential population explosions that might result in outbreaks of dengue."

In addition to El Nino-fueled epidemics of dengue that may occur in regions of the world already infested with Aedes aegypti, another fear, Hopp said, is that climate events like El Nino may help the spread of the mosquito from the tropics and subtropics to more t
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Contact: Marianne Hopp
mhopp@students.wisc.edu
608-265-8720
University of Wisconsin-Madison
4-Aug-1998