The state's Mosquito Management Program said Wednesday the mosquito sample was taken Aug. 8 in Chester. The species found does not usually bite humans.
West Nile virus has been found in mosquitoes in 40 towns this summer. Those samples were taken from June 27 to Aug. 8.
No human West Nile or EEE cases have been reported this year. There were nine West Nile cases last year.
People are advised to wear protective clothing and repellent against mosquitoes and avoid exposure during nighttime hours when mosquitoes are most active.
They also are advised to keep horses vaccinated against the diseases and seek veterinary attention when a horse appears sick.
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