A man in his 60s from Worcester County has become Massachusetts' seventh human case of West Nile virus this year, according to health officials. All six prior cases this season involved residents exposed in Middlesex and Suffolk counties.
The Massachusetts Department of Public Health announced the case on September 11, as reported by WCVB. Prior to this diagnosis, all six of the state's 2026 human cases had occurred in residents exposed in Middlesex and Suffolk counties, according to the Massachusetts Department of Public Health. Public Health Commissioner Robbie Goldstein said mosquitoes remain active and West Nile virus continues to spread, per WCVB.
Mosquito Activity Spans Nearly the Entire State
The human case comes amid what state officials describe as widespread mosquito infection across Massachusetts. As of September 11, 307 mosquito samples had tested positive for West Nile virus across 13 counties since the season's first positive pool turned up on June 16, the state health department reported. Risk levels were elevated to moderate across most of Massachusetts as of that date, with high risk persisting in Boston, Brookline, Cambridge, Chelsea, Everett, Malden, Newton, Revere, Somerville, Watertown, and Winthrop, per WCVB.
Only Dukes and Nantucket counties, along with the Cape Cod towns of Provincetown and Truro, remained at low risk as of the same date, the state agency's report noted. That leaves nearly every other corner of Massachusetts under some elevated level of concern heading into mid-September.
How This Year Compares to Recent Seasons
Seven confirmed human cases through mid-September puts 2026 below the 19 cases Massachusetts recorded in all of 2024 and the nine cases recorded in 2025, according to the Town of Saugus. Human infections began in 2001, and more than 275 Massachusetts residents have been infected with West Nile virus.
Nationally, the picture looks more severe. Early September CDC surveillance data relayed by Patch counted 407 human West Nile virus cases across 40 states, suggesting higher infection activity nationwide than seen in more than two decades.
Understanding the Health Risks
Most people infected with West Nile virus never notice. CDC estimates cited by the American Medical Association indicate roughly 80% of infections are asymptomatic, about 20% cause mild fever, and fewer than 1% progress to severe neuroinvasive disease such as encephalitis or meningitis — conditions that carry a 10% mortality rate and disproportionately affect older or immunocompromised adults.
West Nile is not the only mosquito-borne threat circulating in Massachusetts this year. Fourteen mosquito samples have tested positive for Eastern Equine Encephalitis, though no human or animal EEE cases have been reported through mid-September, per the state health department. EEE is far rarer than West Nile but significantly deadlier: Massachusetts recorded four human EEE cases and one death in 2024, and 12 human cases with six deaths in 2019, according to the same state data.
Precautions and the Path to Frost
Health officials are urging residents to wear long sleeves and pants outdoors to reduce exposed skin, use mosquito repellent, stay mindful of peak mosquito hours, and drain standing water around their homes, according to WCVB. Officials say the risk will persist until the first hard frost, though it remains an open question whether autumn temperatures will bring an early freeze or allow transmission to continue into late September.
Regional mosquito control in Massachusetts operates under Chapter 252 of the Massachusetts General Laws, overseen by the State Reclamation and Mosquito Control Board through local districts that handle larviciding and catch-basin treatments, according to the Central Massachusetts Mosquito Control Project. Residents can opt out of wide-area pesticide spraying on their property through the state Department of Agricultural Resources under 333 CMR 13.03, though those opt-outs can be overridden during a declared public health emergency.
This case follows two earlier 2026 infections Hoodline has tracked closely this summer, including a Middlesex County man in his 90s confirmed as the state's first case and a Middlesex County man in his 60s confirmed as the second. With the virus now confirmed in a seventh resident and mosquito samples testing positive across nearly every county, state officials continue to frame the outbreak as an active, statewide concern rather than one confined to any single region.
