Wisconsin reports first 2026 West Nile virus activity in mosquitoes and a wild bird
Wisconsin has recorded its first confirmed West Nile virus activity of 2026, with positive tests in mosquitoes collected in Milwaukee County and in a wild bird from Bayfield County, the state Department of Health Services announced July 14.
The findings confirm that West Nile virus is circulating in Wisconsin’s mosquito and bird populations. The Department of Health Services said no human West Nile virus cases had been reported in the state at the time of its announcement.
The report names two counties on opposite sides of the state: Milwaukee County in southeastern Wisconsin and Bayfield County in northwestern Wisconsin. The announcement identifies positive mosquito samples from Milwaukee County and one positive wild-bird sample from Bayfield County.
What Wisconsin health officials confirmed
The July 14 announcement marks the first confirmed West Nile virus activity reported by Wisconsin DHS for 2026. It does not report illness in a Wisconsin resident.
The agency’s finding in Milwaukee County is based on mosquitoes that were collected and tested positive. The finding in Bayfield County is based on a wild bird that tested positive.
Those results establish the presence of the virus in the tested mosquito and bird samples. They should not be read to mean that every mosquito in Milwaukee County carries West Nile virus, or that the virus has been found in all parts of either county.
The release does not state how many mosquitoes tested positive, how many mosquito samples were tested, or what type of wild bird tested positive. It also does not provide additional positive-bird totals beyond the described Bayfield County sample.
No human cases reported at time of release
As of the July 14 release, Wisconsin DHS reported zero human West Nile virus cases in the state. That status is tied to the date of the announcement and does not establish whether human-case reporting changed after July 14.
The department’s report is a confirmation of virus activity in mosquitoes and a bird, not a declaration of an outbreak. The available announcement does not provide epidemiological information that would support describing the situation that way.
Still, the identified samples matter because they show that virus-carrying mosquitoes are present in Wisconsin. DHS described the development as the first confirmed activity of the year, placing it within a seasonal risk period for people and animals.
What remains unknown
The state announcement provides a limited snapshot rather than a statewide count of virus activity. It identifies two positive findings in two named counties, but it does not say how broadly the virus is distributed elsewhere in Wisconsin.
It also does not identify additional affected counties, report positive tests from other mosquito collections or birds, or provide a forecast about future human cases. No estimate of the number of people or animals potentially affected was included.
Residents should distinguish between the confirmed facts and what has not been established. Wisconsin DHS confirmed positive mosquito samples in Milwaukee County, a positive wild bird in Bayfield County and no reported human cases as of July 14. The release does not say that a Wisconsin resident became ill, that all local mosquitoes carry the virus, or that an outbreak is underway.
Next known step
The department’s announcement does not specify a future reporting date, a new deadline or a scheduled public update. The next known development would be any subsequent state reporting on West Nile virus activity or human cases.
For now, the July 14 report stands as Wisconsin’s first confirmed West Nile virus activity of 2026: positive mosquitoes in Milwaukee County and a positive wild bird in Bayfield County, with no human cases reported at the time.
Sources
- First Confirmed West Nile Virus Activity in Wisconsin, Wisconsin Department of Health Services