Where to find data

Ongoing information

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.

See spraying (“adulticide events”) in Chester County here. This site is updated relatively quickly but can fall behind the press releases.

See accumulated Chesco Health Department News Releases (including about mosquito spraying) here. This site is not updated as quickly as the state site above.

See Chesco West Nile virus surveillance data here. As the pop-up message says, data are updated weekly and are cumulative except that the Vector Index is for the past 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 can vary.

See WNV “hot zones” in PA, for the preceding 3 weeks here. Also similar information for previous years.

See and sign up for a daily (on weekdays) report on WNV-carrying mosquitoes trapped in each county here.

Summer 2017

Statewide WNV data by county here. Per data available on October 4, there have been 155 Chester County positives out of 738 samples tested in 2017. Meanwhile, there have been 12 known human cases in PA, 3 of them in Chester County, and no WNV-caused deaths in the state (compare to well over 2,000 annual opioid-related deaths in PA).

There have been five Chesco “spraying event” so far in 2017, in Phoenixville, Downingtown, East Caln, Thornbury/Birmingham, and East Bradford (see details under Ongoing Information above).

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.