Varying effects of climate change.

• Position: West Nile Virus

The varied influence of climate change on temperature and precipitation may have an equally wide-ranging effect on the spread of West Nile virus, suggesting that public health efforts to control the virus will need to take a local--rather than global--perspective, according to a study published in the Proceedings of the National Academy of Sciences.

Researchers Cory Morin and Andrew Comrie have found that, under the future climate conditions predicted by climate change models, many locations will see a lengthening of the mosquito season, but shrinking summer mosquito populations due to hotter and dryer conditions allowing fewer larvae to survive.

However, these changes vary significantly depending on temperature and precipitation. For example, drops in summer mosquito populations are expected to be significant in the South, but not farther north where there still will be enough rain to maintain summer breeding habitats and extreme temperatures are less common. These findings suggest that disease transmission studies and programs designed to control populations of disease-carrying mosquitoes must be targeted locally to maximize their effectiveness, the authors contend.

"It used to be an open question whether climate change is going to make disease-carrying mosquitoes more abundant, and the answer is it will depend on the time and the location," maintains Morin. "One assumption was that, with rising temperatures, mosquitoes would thrive across the board. Our study shows this is unlikely. Rather, the effects of climate change are different depending on the region and, because of that, the response of West Nile virus transmitting mosquito populations will be...