West Nile Season Is Surging in Chicago’s Trap Ledger: 187 Positive Pools So Far, the Fourth-Most at This Point in Twenty Seasons

Chicago's own mosquito-trap ledger, twenty seasons deep: 187 positive West Nile pools so far in 2026 - the fourth-most through week 32 in the file, behind 2012, 2016, and 2025 - with the weekly surge charted. Trap-pool tests, never human cases, and the boundary holds on every number.









