The outbreak, which has surged since late July, is concentrated in southwestern Wisconsin and neighboring counties. According to the Wisconsin Department of Health Services, Grant County has the most cases with 153, followed by Lafayette County with 122 and Iowa County with 97. Smaller clusters have been reported in Vernon (14), Sauk (10), Rock (5), and Richland (1) counties.

The death of an infant last week marked a grim milestone for a state that had not seen a measles fatality in more than three decades. Health officials have not released additional details about the infant.

Measles is one of the most contagious viruses known to science. It spreads through the air when an infected person coughs or sneezes, and the virus can linger in the air for up to two hours after the person has left the room. Symptoms typically appear 10 to 12 days after exposure and include a runny nose, high fever that can exceed 104°F, fatigue, cough, and red, watery eyes. A red rash usually begins at the hairline and spreads to the arms and legs.

Health officials are urging anyone who develops symptoms to stay home and call a healthcare provider before visiting a clinic, to avoid exposing others in waiting rooms.

The best protection against measles is vaccination with the two-dose measles, mumps, and rubella (MMR) vaccine, which is highly effective at preventing infection and reducing the severity of illness in those who do contract the virus.

The outbreak's rapid growth has raised concerns about vaccination rates in the affected communities. Public health experts say high community immunity—typically achieved when at least 95% of the population is vaccinated—is necessary to prevent sustained transmission.

State and local health departments are continuing to monitor the situation and provide updates as new cases are confirmed. Residents are encouraged to check their vaccination status and contact their healthcare provider if they have questions.