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The Philadelphia Department of Public Health (PDPH) identified the first symptomatic West Nile virus (WNV) infection for the 2025 season in an adult resident who developed WNV fever symptoms in late June or early July. Potential exposures occurred outside of Philadelphia.
The WNV pool positivity in 2025 is higher than the year-to-date historic median rate from 2001-2024 (17% vs 7%) and similar to rates observed in 2010, 2018, and 2022 (16%-42%), peak WNV activity seasons in Philadelphia. Increased risk for human infection will continue in Philadelphia until the first hard frost occurs.
From May through October, PDPH, in collaboration with the PA Department of Environmental Protection, conducts mosquito management activities throughout Philadelphia, which entails surveillance and identification of mosquito pools, testing pools for WNV, and control activities (eliminating breeding sites, larviciding catch basins, ground spraying, etc.). Since May 2025, 63 mosquito larvicide treatment events have been conducted across Philadelphia, and five locations were treated to control adult mosquito populations.
Click here to download the latest 2025 West Nile Virus report in a printable format.
Week 33 (8/10 - 8/16) |
2025 Season (5/1 - 8/16) |
|
---|---|---|
Mosquito Pools Tested* |
41 |
454 |
WNV Positive Pools |
15 |
85 |
Human WNV Cases |
0 |
1 |
Neuroinvasive WNV |
0 |
0 |
WNV Fever |
0 |
1 |
Human WNV Deaths |
0 |
0 |
Presumptive Viremic Donors |
0 |
0 |
*454 mosquito pools at 88 different mosquito trapping sites
State and National WNV Activity Reports
Advise your patients to:
WNV Testing and Reporting Requirements for Human Surveillance in Philadelphia: