West Nile Virus is transmitted by mosquitoes and causes an illness that ranges from mild-to-severe.  Mild, flu-like illness is often called West Nile fever.  More severe forms of disease, which can be life-threatening, may be called West Nile encephalitis or West Nile meningitis, depending on where it spreads.  Mosquitoes carry the highest amounts of virus in the early fall, thus there is a peak of disease in late August to early September.  The risk of disease then decreases as the weather becomes colder and mosquitoes die off.

Click here to visit Pennsylvania's West Nile Virus Control website.