​In 2000, West Nile Virus appeared in Pennsylvania for the first time. To help detect, track and control the virus, the Pennsylvania departments of Health, Environmental Protection (DEP) and Agriculture developed a comprehensive surveillance program. Pennsylvania's plan uses the principles of Integrated Pest Management (IPM) and focuses on education, habitat reduction, surveillance, and control.

The Department of Health is conducting laboratory testing to confirm West Nile Virus cases, and monitoring any possible human cases. In addition, it has been working with healthcare providers across the state to educate them about the signs and symptoms of West Nile Virus.

DEP coordinates the Commonwealth's mosquito control program with representatives from 38 counties at the highest risk of mosquito-borne disease to develop a comprehensive mosquito surveillance and control network. The foundation of this collaborative effort is based on integrated pest management principles. Since the virus is transmitted by mosquitoes, early detection and control are key. The program is a gold member of EPA's pesticide environmental stewardship program. The Department of Environmental Protection, with the support of the legislature, provides funding to this network of counties to protect against disease and alleviate public nuisances.

The Department of Agriculture is monitoring animal populations for any signs of the virus. Due to the impact of WNV on the ruffed grouse, the Pennsylvania Game commission collaborates with the PA program to track the intensity of seasonal WNV. Seasonal data is used, in part, to determine hunting season length of the ruffed grouse.

Since 2000, Pennsylvania's State budget has included funding to prevent and mitigate the potential public-health effects of West Nile on the citizens of the Commonwealth. The funds provide necessary staffing and an improved epidemiological infrastructure to monitor and control the virus. This network, which covers 38 counties, includes mosquito and bird surveillance and monitoring people and horses. Please explore our site to find out more about how you can help reduce your risk of disease exposure, to learn about West Nile Virus or the latest surveillance update from your area.

DEP Vector Management staff services a mosquito trap in a residential neighborhood in Dauphin County

Please Note: The PA West Nile Virus Control Program is not a hospital or clinical facility; we do not see patients and are unable to diagnose your illness, provide treatment, prescribe medication, or refer you to specialists. If you have a medical emergency, contacting the PA WNV Control Program is not the proper way to get immediate help. If you are a patient, please see your health care provider or the nearest emergency room. If you are a health care provider, please contact your state epidemiologist or local health department.

Commonwealth of Pennsylvania WNV Plan 2022

​West Nile Virus is a mosquito-borne disease that can cause encephalitis, a brain inflammation and is typically spread by the bite of a mosquito. West Nile Virus was first detected in North America in 1999 and found in Pennsylvania in 2000. Prior to that, it had only been found in Africa, Eastern Europe, and West Asia.

In Pennsylvania, West Nile Virus maintains itself in nature by cycling between mosquitoes in the genus Culex and certain species of birds. A mosquito (the vector) bites an uninfected bird (the host), the virus amplifies within the bird, an uninfected mosquito bites the bird and is in turn infected. This cycle compounds itself through summer and fall, increasing the likelihood of someone being bitten by a diseased mosquito.

West Nile Fever and Encephalitis

West Nile fever is a case of mild disease in people, characterized by flu-like symptoms. West Nile fever typically lasts only a few days and does not appear to cause any long-term health effects. More severe diseases due to a person being infected with this virus can be “West Nile encephalitis,” West Nile meningitis or West Nile meningoencephalitis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it.

How can I get West Nile Virus?

The principal route of human infection with West Nile virus is through the bite of an infected mosquito. Additional routes of infection have become apparent as scientists and physicians continue to study the virus, they include blood transfusion and organ transplantation. It is important to note that these other methods of transmission represent a very small proportion of cases. Other methods of transmission include blood transfusion, organ transplantation, mother-to-child (ingestion of breast milk and transplacental) and occupational.

​All residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis; persons over 50 and immunocompromised individuals are at increased risk for WNV disease.

What are the symptoms?

People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands. Most people who are infected with the West Nile Virus will not have any type of illness. It is estimated that 1 in 5 people who become infected will develop West Nile fever: mild symptoms, including fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands.

The symptoms of severe infection (West Nile encephalitis or meningitis) include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. It is estimated that 1 in 150 persons infected with the West Nile Virus will develop a more severe form of disease.
Symptoms of mild disease will generally last a few days. Symptoms of severe disease may last several weeks, although neurological effects may be permanent.

Is there treatment or a vaccine?

There is no specific treatment or vaccine for West Nile Virus infection. Most people fully recover from the virus. In more severe cases, intensive supportive therapy is indicated, often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.

​Did you know that standing water in something as small as a bottle cap can provide enough space for a mosquito egg raft? This tiny raft of eggs can produce as many as 300 mosquitoes.  

Turn over plastic wading pools when not in use. Stagnant water in a wading pool becomes a place for mosquitoes to breed.

Dispose of tin cans, plastic containers, ceramic pots or similar water-holding containers that have collected on your property.

Turn over wheelbarrows and don't let water stagnate in birdbaths. Both provide breeding habitats for domestic mosquitoes.

Aerate ornamental pools or stock them with fish. Water gardens can become major mosquito producers if they are allowed to stagnate. Clean and chlorinate swimming pools not in use.  Mosquitoes may even breed in the water that collects on pool covers.

Pay special attention to discarded tires. Stagnant water in tires is an excellent habitat for mosquitoes to thrive.

Eliminating tires from urban environments is critical to reducing mosquito populations associated with transmitting diseases from mosquitoes.

​If West Nile virus is found in your area, here are some ways you can protect yourself:

Wear shoes, socks, long pants and a long-sleeved shirt when outdoors for long periods of time, or when mosquitoes are most active. Mosquitoes are most active at dusk and dawn, although the invasive Asian tiger is known to bite predominately during daylight hours.

Consider the use of mosquito repellent, according to directions, when it is necessary to be outdoors. Wash all treated skin and clothing when returning indoors.

​DEP and county mosquito control professionals have been using Bacillus thuringiensis israelensis (Bti), a naturally occurring soil bacteria. This material is now becoming widely available for you to buy and use yourself at home.

Bti can be purchased in small, donut-shaped form, often called "mosquito dunks", which are useful in small areas of standing water, such as a birdbath or small puddle of water that may gather in a low spot on your property. A granular form of Bti is available and effective for larger areas, such as backyard ponds.

Bti can be purchased in many lawn and garden, outdoor supply, and home improvement stores. The great thing about this bacteria is that it kills only mosquito and black fly larvae. It is not harmful to people, pets, aquatic life (such as fish) or plants.

The best way to control mosquitoes is to eliminate standing water on your property. If you do decide to use mosquito dunks, make sure to follow label and application instructions.

Something as innocuous as this ornamental pond can produce millions of mosquitoes capable of transmitting disease. Ornamental ponds with permanent standing water should be aerated or treated with Bti to reduce mosquito bites and West Nile Virus transmission.

West Nile Virus has been detected in a variety of bird species. Some infected birds, especially robins, crows, jays, and raptors are known to get sick and die from the infection. Reporting and testing of dead birds is one way to check for the presence of West Nile Virus in the environment. Incidents of dead or sick birds involving robins, crows, jays or raptors can be reported on this website or to your local county WNV coordinator.

West Nile Virus is transmitted to birds through the bite of infected mosquitoes. Mosquitoes become infected by biting infected birds. Some birds that are predators (such as hawks and owls) or scavengers (such as crows) may become infected after eating sick or dead birds that were already infected with West Nile Virus.

How You Can Help With Dead Bird Reporting

Reporting of dead birds is a good way to check for West Nile Virus activity in the environment and allow implementation of prevention and control measures to minimize the spread of the virus. The Pennsylvania Surveillance program relies on citizens to report dead birds to their West Nile county coordinator or by using the reporting tool on this website. Since the virus was detected in New York City in 1999, thousands of dead birds have been submitted for testing by citizens in the northeastern US. 

St. Louis Encephalitis (SLE)

• SLE virus is also spread by the bite of infected mosquito (primarily Culex pipiens & Culex quinquefasciatus in the eastern states).
• The most common bird hosts are sparrows, pigeons, blue jays and robins.
• Most cases have occurred in Eastern and Central states in late summer or early fall.
• Most people that become infected do not have symptoms, but those who do become ill could develop neuroinvasive disease such as encephalitis or meningitis.

• Eastern Equine Encephalitis (EEE) virus is also spread to people by the bite of an infected mosquito.
• Only a few cases are reported in the United States each year, with the majority occurring in the eastern or gulf coast states.
• Approximately 30% of people with EEE die and many survivors have ongoing neurological problems.

• In Africa these viruses are transmitted between Aedes mosquitoes and primates- sporadic human infection.
• In an urban setting these viruses are maintained in a human-mosquito-human transmission cycle.