DEP: Rains, flooding create high level of West Nile in PA’s mosquitos

HARRISBURG — Receding floodwaters and heavy rains across Pennsylvania are creating a perfect storm of conditions, that have contributed to the highest level of West Nile virus activity in the mosquito population since the disease was first introduced in 2000. The disease, which has infected more than 150 people in the past six years, is on track to pose an unusually higher than normal risk this year and is widespread throughout the commonwealth, having already been found in 51 Pennsylvania Counties as of August 1, 2018. 

“With record levels of West Nile virus activity in mosquitoes already found, we are at increased risk of disease from a bite of a mosquito. It is imperative that Pennsylvania residents take common-sense precautions to protect themselves from mosquitoes,” said DEP Secretary Patrick McDonnell. “There has been one human case already this year. Our goal is for that to be the only one. By eliminating places for mosquitoes to lay eggs, using insect repellant and other protective measures, and targeted use of pesticides, we can all make sure Pennsylvanians are protected.”
Governor Wolf’s administration is taking several specific initiatives to combat this little-known virus. The Pennsylvania Department of Health has issued an advisory through the Health Advisory Network to alert medical professionals about the risk of West Nile virus this year. Governor Wolf and the legislature also recently approved a $140,000 increase to the program’s budget.
DEP West Nile virus program staff have conducted multiple operations to reduce mosquito habitats from tire piles and other areas. These efforts will be ongoing until the first hard frost of the year.
The virus can have devastating effects on bird populations as well. Pennsylvania’s state bird, the ruffed grouse, has been hit especially hard by the virus, and the winter hunting season for the bird has been curtailed as a result of the virus and habitat loss.
“The disease is especially deadly to birds, including grouse,” said Matt Helwig, a biologist with the DEP mosquito program
Residents can also eliminate habitat by getting rid of standing and stagnant water where mosquitoes lay eggs.
“Mosquitoes are weak flyers and won’t travel far from where they are born – if there are mosquitoes in your backyard or neighborhood, they are likely laying eggs there as well,” said Helwig, “If you’re being bitten by mosquitoes, they are 9 times out of 10 coming from your property. Get rid of even small amounts of standing water around your home.”
Common places water can accumulate are outdoor features like potted plants and birdbaths, yard debris like, storage bins, kids’ toys (including kiddie pools), rain gutters, and even corrugated downspouts.
“It doesn’t take much for several hundred mosquitoes to be born. The small pool of water that collects in a single upturned bottle cap is an incubator for as many as 300 mosquito eggs,” said Helwig. Mosquitoes acquire the virus by biting infected birds and transmit the virus to people through a subsequent bite.
Use of commonly sold insect repellants, like those using DEET, Picaridin, or other EPA-registered repellants, can also cut down on mosquito bites, and possible exposure to the virus. Long pants and sleeves are also an important way to cut down on possible exposure to mosquitoes.
DEP and county partners throughout the state will also conduct routine, localized spraying events to control infected adult populations of mosquitoes. These operations are conducted when and where deemed necessary based on recent population survey results.
“Control operations are a strong tool, but they are not a substitute for preventive measures like eliminating standing, stagnant water,” said Helwig.
Symptoms of West Nile virus in humans are typically like those of a mild flu, but the virus can lead to a more serious condition that includes swelling of the brain, muscle convulsions, coma, paralysis, and death. Since DEP first began monitoring for the virus in 2000 there have been 33 fatal cases of West Nile virus in Pennsylvania.
“While the symptoms may not seem threatening in the vast majority of cases, serious impacts to health can occur from being bitten by mosquitoes that carry this virus,” said McDonnell.
For more information on West Nile virus please visit
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One Comment

  1. Yes, people should eliminate standing water in which mosquitoes breed. Tip: don’t forget clogged or ill-draining eaves at roof level. But is this a public health crisis? Should a lot of public money be going into widespread pesticide spraying? Number of drug overdose deaths in Chester County according to OverdoseFreePA, total, 2015-18 so far: 391. West Nile Virus: 0. Damage from pesticide spraying: TBA.

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