Overview

• Chicago Department of Public Health confirmed three residents aged 40 to 80 as the city’s first human West Nile virus cases of 2025.
• Recent testing found nearly half of mosquito pools positive for the virus, driving CDPH to classify Chicago’s risk level as “high.”
• Licensed abatement teams will conduct ultra-low-volume insecticide spraying in seven neighborhoods this week and maintain weekly mosquito surveillance through October.
• Massachusetts Department of Public Health raised its West Nile risk to “high” in Boston and surrounding towns after detecting 168 positive mosquito samples, though no human cases are reported.
• Officials urge use of EPA-registered repellents, wearing protective clothing during peak mosquito hours, and eliminating standing water to reduce transmission risk.