The Philadelphia Department of Public Health (PDPH) has identified three positive cases of West Nile virus (WNV) infections in Philadelphia. All of the three positive cases suffered some degree of neurological complications. One asymptomatic presumptive viremic blood donor was also identified. Here’s what you need to know about this pesky virus.
West Nile Virus In Philadelphia
Every year, The Philadelphia Department of Public Health (PDPH) routinely tests mosquitoes pools in our area. This year however, the positivity rate is much higher compared to year’s past. According to data released by the PDPH, the WNV pool positivity in 2024 is higher than the year-to-date historic median rate from 2001-2023 (45% vs 7%) and higher than rates observed in 2010, 2018, and 2022 (18%-44%), peak WNV activity seasons in Philadelphia.
As a result, Increased risk for human infection will continue in Philadelphia and the surrounding regions until the first hard frost occurs.
What is West Nile virus?
West Nile virus is a mosquito-borne illness. This disease is spread to people by the bite of an infected mosquito. West Nile is the leading cause of mosquito-borne illness across the continental United States. Cases of West Nile occur during mosquito season, which starts in the summer and continues through fall or until the first hard frost. At this time, there is no vaccine.
What are the symptoms of West Nile virus?
West Nile virus is a common mosquito-borne disease. Most people who are bitten by an infected mosquito will not get sick or suffer any noticeable symptoms. Specifically, according to the CDC, only about 1 in 5 people who are infected develop a fever and other symptoms.
Is WNV deadly?
It can be. However, death resulting from a West Nile infection is rare. In fact, according to the CDC, only 1 in every 150 people infected develop a serious, sometimes fatal, illness. Severe symptoms that affect the central nervous system, such as brain and spinal cord inflammation, include high fever, headache, confusion, muscle weakness, stiff neck, numbness, tremors, and vision loss.
While most people recover from a severe illness, some may suffer permanent effects.
About 1 in 10 people who develop a severe neuroinvasive illness, will die.
People age 60 and older are at greater risk of developing a severe illness due to West Nile virus.
Are there preventative measures I can take to protect myself ?
Yes. The Philadelphia Department of Public Health recommends the following:
- Use repellent with DEET (≥ 20% to also prevent tick bites), Picaridin, or oil of lemon eucalyptus when outdoors.
- Regularly check and remove standing water outside their home (e.g., unused pools, tires).
- Keep well-fitted screens on windows and doors.
- Report mosquito problems and dead bird sightings to the PDPH Vector Control Program’s Mosquito Complaint hotline at 215-685-9000.