Several dozen mosquitoes have tested positive for West Nile virus in 15 Pennsylvania counties so far this year. According to the state Department of Environmental Protection, that prevalence is about one month earlier than last year. DEP spokesman Tom Rathbun says the warm, wet weather may have contributed to speeding up the virus’s appearance. “We’re not sure yet at this point if it means we’re seeing a larger outbreak or not. I don’t think so at this point. I think we’ve come to accept that in the southeastern part of Pennsylvania, West Nile has become endemic and we can expect to see it there every year,” Rathbun says. The counties with infected mosquitoes include Philadelphia, Delaware, Bucks, and Montgomery — where one person has also tested positive this year. The DEP urges residents to clear any standing water and use bug spray to prevent bites.