Ongoing information

See all PA DEP WNV-related news releases, going back to 2000, here. To the left there you can click to download data for all prior years.

The PA DEP’s main public WNV info page is here. About 1/3 of the way down this large and confusing page, see the statewide map of “Current Counties Positive of West Nile Virus.” To the left you can download data for all counties for each year since 2000.

Just below that see the map of “Recent West Nile Virus Hot Zones.”

Below that map you can click to download “2019 spray events.”

See Chester County info on Mosquito-borne Diseases here, with links but no data.

See recent Chesco Health Department News (including about mosquito spraying) here. There no longer seems to be a single site for all mosquito-related releases.

Sign up to receive Chesco Public Health updates here. This is the fastest way to receive information. Please encourage your municipality to post these releases on receipt on their own web site. We can no longer find these releases archived on the Chester County web site.

Through 7/30/18, Chesco West Nile virus surveillance data by municipality could be found here. Till then, data were updated weekly and were cumulative except that the Vector Index was for the previous 3 weeks. The Vector Index is a score based on the number of WNV-positive traps and the total number of traps. The Vector Index at which the County decides to spray a given location varies for unknown reasons. These data remain valuable for purposes of comparison over time, but we do not know why the County has decided that the public (that’s anyone reading this) and municipal governments no longer deserve access to this information that is vital for planning for mosquito control.

See WNV “hot zones” in PA, for the preceding 3 weeks here. Also similar information for previous years. This site has unfortunately not been updated since 8/14/18.

See and sign up for a daily (on weekdays) report on WNV-carrying mosquitoes trapped in each county here. You can also see occasional reports (marked Summary), especially at the end of the season, showing the number of human, avian, and mosquito WNV positives for each county.

Summer 2018

Several of the DEP sites seem to have suffered a breakdown in the middle of the 2018 mosquito season, so we were not able to follow the numbers as we would have liked. The 2018 data download (2nd paragraph above) shows Chesco had 6 (presumed) human cases out of 130 in the state. We have not heard of any 2018 WNV deaths in PA.

There were huge numbers of mosquito pools testing positive, so it is obvious that mosquitoes do not transmit WNV to humans effectively and/or humans resist WNV without diagnosis.

Summer 2017

Statewide WNV data by county here. There were 156 Chester County positives out of 751 mosquito pools tested in 2017. Meanwhile, there were 20 known human cases in all PA, 4 of them in Chester County (however, “*This number may include positive cases for pathogens other than West Nile Virus”), and no WNV-caused deaths in the state (compare to well over 2,000 annual opioid-related deaths in PA).

There were 5 Chesco “spraying events” affecting 7 municipalities in 2017, in Thornbury/Birmingham. Downingtown/East Caln, Phoenixville, East Bradford, and Spring City. You can see the press releases by searching our site.

Summer 2016

See statewide data on West Nile virus by county here. In 2014-15-16, Chester County had a total of 3 known human cases and no known WNV-related deaths.

In 2016, 4 Chesco releases concerned mosquitoes and WNV, including 2 about spraying. See here.