September 04, 2026
Nick King/USA TODAY NETWORK via Imagn Images
Philadelphia has reported four West Nile Virus cases this year. The mosquito-borne illness can cause flu-like symptoms or death in some cases.
Philadelphia reported four cases of West Nile Virus, a mosquito-borne illness that affects the central nervous system, on Friday. The cases are the first of the year.
The infection often does not present any symptoms, but 1 in 5 people experience fever and flu-like symptoms. About 1 in every 150 people develop a severe case that can cause brain or spinal inflammation and sometimes death. People 55 and over, those who have received organ transplants or have other underlying medical conditions are more likely to develop a serious case.
Health officials did not provide any information about the four cases. Mosquitos carrying the virus have been reported in 46 of Pennsylvania's 67 counties, the Pennsylvania Department of Environmental Protection says. Another two human cases have been reported in Allegheny County.
There are more than 3,000 mosquito species in total, but only 200 exist in the United States and 60 in Pennsylvania. The most common in urban areas is the northern house mosquito, which is thought to transmit most of the West Nile cases in the area.
There is no cure or vaccine for West Nile, but most people who have had it are protected from additional infections.
Mosquitos can breed in as little as 1 inch of standing water. The city's Vector Control Services sprays insecticide to prevent mosquitos at parks and other public spaces and also treats storm drain outlets to prevent breeding. Residents can call the Mosquito Complaint Hotline at (215) 685-900 to report a mosquito infestation. City officials will inspect the location and treat it, if necessary.
Health officials also asked residents to help prevent mosquitos in their backyards and porches. Here's how to protect your home:
• Remove any unnecessary objects that can hold standing water, including unusual items like soda caps and discarded tires.
• Empty water from flower pots, pet food, water bowls, birdbaths, swimming pool covers, buckets and more at least once or twice a week.
• Empty wading pools for kids when not in use.
• Clean out clogged rain gutters.
• Aerate ponds or add fish.
• Keep tight screens on windows and doors.
Because it's difficult to completely avoid insects, health officials also recommend people wear insect repellent and long clothing outside. To avoid bites, residents also are advised to stay indoors around dawn and dusk. Repellents should contain DEET, Picaridin, eucalyptus oil or PMD.
"We all have a role in preventing the spread of West Nile Virus," Health Commissioner Palak Raval-Nelson said in a statement. "And it's easy to do: Wear mosquito repellent and dump out standing water."
