Overview

• Delaware County confirmed its first human case this year, the sixth reported across the Philadelphia region, with no details released on the patient’s age, gender, or residence.
• Massachusetts reported its first human infection of 2025 in a woman in her 70s who was exposed in Middlesex County, according to the state health department.
• Surveillance remains elevated, with 108 West Nile–positive mosquito samples in Delaware County and 319 in Massachusetts across 12 of 14 counties.
• Authorities advise EPA-registered repellents, long sleeves, avoiding dusk-to-dawn outdoor activity, and eliminating standing water, noting mosquitoes will persist until a hard frost.
• Most infections are asymptomatic, about 20% cause flu-like illness, fewer than 1% lead to severe neurologic disease, and last year saw four deaths in the Philadelphia region.