WEST WHITELAND >> The Pennsylvania Department of Environmental Protection announced one mosquito sample taken in the county tested positive for West Nile virus Friday.
The sample, taken in West Whiteland, is the second positive confirmation of the virus in Chester County this year. Samples from Tredyffrin tested positive earlier this year in July.
According to the Centers for Disease Control and Prevention (CDC), the virus is most commonly transmitted to humans through mosquito bites.
For that reason, the CDC recommends using bug spray when going outside in areas where there is a confirmed presence of the virus, and for homeowners to actively remove standing water on their properties.
Most people infected with the virus (between 70 and 80 percent) show no symptoms, whereas roughly 20 percent of people infected can develop a fever, joint pain, vomiting and diarrhea.
The CDC states less than 1 percent of those infected will develop a serious neurological illness. Of that 1 percent, 10 percent of those will die, the CDC estimates.
In 2015, the Pennsylvania West Nile Virus Control Program collected 124 total positive samples of the virus in Chester County, and reported two human cases, a sharp increase from 2014, where 52 total positives were collected and no human cases were reported.
Prior to 2015, the last reported human case was in 2012.
The CDC states on their website that there is no vaccine or specific antiviral treatment for the disease; however, over-the-counter pain relievers can help mitigate some symptoms. In severe cases, hospitalization is necessary.
West Nile virus first appeared in the United States in the New York City area in 1999, where eight people fell ill with the disease, according to an article in the New England Journal of Medicine.
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