DEP: Perfect storm for West Nile virus in Pennsylvania

HARRISBURG – Pennsylvania is seeing its highest level of West Nile virus activity in mosquitoes since the disease first appeared in the state 18 years ago.

 “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 Matt Helwig, a biologist with the DEP mosquito program. “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.”

Receding floodwaters and heavy rains across Pennsylvania are creating a perfect storm for mosquito breeding, according to state Environmental Protection Secretary Patrick McDonnell.

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Technicians across the state are collecting adult mosquitoes and testing them for the presence of the virus. Franklin County ranks 11th in the state this year with 49 mosquito samples testing positive. Delaware and York counties with 140 and 136 samples, respectively, rank No. 1 and 2.

The disease, which has infected more than 150 people in Pennsylvania in the past six years, poses an unusually higher than normal risk this year, according to McDonnell.

“It doesn’t take much for several hundred mosquitoes to be born,” Helwig said. “The small pool of water that collects in a single upturned bottle cap is an incubator for as many as 300 mosquito eggs.”

Much of the state in July saw at least twice as much rainfall as normal.

Franklin County's most recent human case of West Nile was in 2014. The virus contributed to the death of a local elderly woman in 2005.

The state has had one human case so far this year, an elderly man in Allegheny County.

“Our goal is for that to be the only one,” McDonnell said. “By eliminating places for mosquitoes to lay eggs, using insect repellant and targeted use of pesticides, we can all make sure Pennsylvanians are protected.”

There were 20 human cases in the state last year.

Mosquito samples taken this season in Chambersburg and Waynesboro and the townships of Greene, Guilford, Hamilton and Washington have tested positive for West Nile.

According to the Centers for Disease Control and Prevention, all residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis. Certain mosquitoes can transmit the West Nile virus to people. The virus can cause West Nile encephalitis, an infection that can result in an inflammation of the brain.

Mosquitos switch from feeding on birds to feeding on people as the birds migrate out of the area in late summer. Mosquitoes acquire the virus by biting infected birds and transmitting the virus to people through a subsequent bite. The season continues until the first hard frost.

“We are at increased risk of disease from a bite of a mosquito,” McDonnell said. “It is imperative that Pennsylvania residents take common-sense precautions to protect themselves from mosquitoes.”

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Residents can eliminate habitat by getting rid of standing and stagnant water where mosquitoes lay eggs. Common places water can accumulate are outdoor features like potted plants and birdbaths, yard debris like, storage bins, children's toys (including kiddie pools), rain gutters and even corrugated downspouts.

DEP and county partners throughout the state are conducting routine, localized spraying to control infected adult populations of mosquitoes. These operations are based on mosquito population survey results.

“Control operations are a strong tool, but they are not a substitute for preventive measures like eliminating standing, stagnant water,” Helwig said.

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. 

“The disease is especially deadly to birds, including grouse,” Helwig said.

Pennsylvania’s state bird, the ruffed grouse, has been hit especially hard by the virus. The winter hunting season for the grouse has been curtailed because of the virus and habitat loss. 

 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. Gov. Tom Wolf and the legislature also recently approved a $140,000 increase to the program’s budget.

West Nile symptoms

Symptoms of West Nile virus can take the appearance 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.