West Nile Virus
Last reported: August 2025
moderate risk
Mosquitoes in Philadelphia, Pennsylvania
4 active species · Season May–Sep · Humid Continental/Temperate climate · Moderate standing-water risk
Active disease alerts
Species active in Philadelphia
Asian Tiger Mosquito
Aedes albopictus
Striking black mosquito with white stripes on legs and thorax. Originally from Southeast Asia, now widespread in North America. Known for aggressive, persistent biting behavior.…
Carries: Dengue Fever · Zika Virus · West Nile Virus
Northern House Mosquito
Culex pipiens
Brown mosquito with banded legs. Common in temperate climates. Often enters homes at night. Prefers standing water with organic matter.…
Carries: West Nile Virus · St. Louis Encephalitis · Avian Malaria
Inland Floodwater Mosquito
Aedes vexans
Medium-sized brown mosquito with white markings. Breeds in temporary, freshwater pools. Emerges en masse after flooding.…
Carries: West Nile Virus · Eastern Equine Encephalitis
Asian Rock Mosquito
Ochlerotatus japonicus
Small, dark mosquito recently introduced to North America from Asia. Adapts well to cold climates. Breeds in container water.…
Carries: West Nile Virus