Weather Predicts West Nile Virus Occurrences

In the US, there is a relationship between the weather and West Nile virus (WNV) disease prevalence—which could be used to forecast outbreaks—according to an article published in The American Journal of Tropical Medicine and Hygiene.

Using data from 2004-2012, a team of investigators at the National Center for Atmospheric Research (NCAR) in CO and the Centers for Disease Control and Prevention (CDC) created a model which identified meteorological anomalies in relation to spikes in WNV frequency. Due to a variation in WNV rates, the researchers divided the US into 10 climate regions.

In doing so, the authors found most areas with above average temperature experienced higher rates of WMV transmission. The investigators also discovered lower precipitation rates drove WMV disease in the eastern US, but this correlation was the opposite in the west.

Moreover, the investigators reported the relationship between temperature and WMV was strongest in northeast and southeast, where a yearly temperature increase of 1.8° Fahrenheit more than the 2004-2012 average was associated with a fivefold risk a WMV outbreak. While this type of spike in temperature doubled the WMV outbreak risk in other locations, the link wasn’t seen in the western US.

The researchers believe weather could influence WMV prevalence in several ways, including affecting the development of mosquito larvae and breeding habitats, according to a statement released by the NCAR and University Corporation for Atmospheric Research.

“We've shown that it may be possible to build a system to forecast the risk of West Nile virus disease several weeks or months in advance, before the disease begins to peak in summer,” the study’s lead author, Micah Hahn, a scientist with NCAR and Centers for Disease Control (CDC), said. “Having advance warning can help public health agencies plan and take additional steps to protect the public.”