Increase in West Nile Virus cases linked to temperatures and rainfall

Increase in West Nile Virus cases linked to temperatures and rainfall

A new study from the National Center for Atmospheric Research and the U.S. Centers for Disease Control and Prevention has found a connection between temperatures and West Nile Virus cases.  They found that hot weather in the months prior to the start of West Nile Virus season (typically June) was correlated with a more severe season for the virus.

The researchers came to this conclusion after analyzing temperature data and West Nile cases for the nine months leading up to the summer virus season, as well as the summer itself.  The researchers found that an average seasonal temperature just 1.8 degrees above normal increased the chance of an above-average West Nile season by five times in the northeast and southeast U.S.  For most of the rest of the country, the same temperature increase doubled the chance of seeing an above average virus season.

Precipitation trends also play a role in the virus season, according to researchers.  They point out that rain tends to decrease West Nile cases along the eastern seaboard, while the west coast tends to see a spike in cases during rainy seasons.  Researchers believe that this difference has to do with the breeding habits of the different species of mosquitos found along the east and west coasts.

The researchers point out that this study is using weather to explain the year to year variation of West Nile cases, which could eventually help to create a seasonal West Nile forecast.  They went on to add that they are not looking to project what West Nile might look like in 5 to 10 years.  More on this study can be found in the American Journal of Tropical Medicine & Hygiene.

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