Oconto County Measles Outbreak: August 22, 2025 Update

This message is being sent to Infection Preventionists and the Health Alert Network.

The Wisconsin Department of Health Services (DHS) and Oconto County Public Health have identified five additional cases of measles in Oconto County. The additional cases are linked to the nine cases confirmed in the county on August 2, 2025, bringing the total number of cases to 14.

DHS is working in coordination with Oconto County Public Health and surrounding local public health departments to identify and directly notify people with known exposures.

At this time, the investigation has not identified locations in public settings for which a full list of exposed people cannot be obtained.

Given the potential for additional cases, we ask that infection preventionists, especially those in the Northeastern Region, share this information within their health care networks.

For health care providers and infection preventionists

Be prepared to care for a patient with suspect measles to help reduce the risk of transmission to others:

• Review policy and procedures regarding intake of a suspect or confirmed measles case. Educate staff on infection prevention and control best practices, including the use of standard and airborne precautions.
  • Only those health care providers who have documented immunity to measles should care for a suspected or confirmed measles case. Documentation of immunity for staff should be collected in advance.
  • Airborne precautions include isolation in a negative air pressure isolation room (AIIR). Have a plan in place if your facility does not have an AIIR.
  • All staff caring for patients with suspected or confirmed measles should wear a fit-tested NIOSH-approved N95 or higher level respiratory even if they have immunity.
  • Have a process to quickly identify and isolate suspected or confirmed measles cases, including appropriate signage and triage processes.
• Contact your local and Tribal health department (LTHD) to facilitate testing. The LTHD will work with the DHS Immunization Program for approval of fee-exempt testing and to arrange logistics for transportation of the specimens to the Wisconsin State Laboratory of Hygiene (WSLH).
• Immediately report by telephone any suspected or confirmed case to the LTHD in which the patient resides.

All health care facilities should have a process to manage exposed health care personnel:

• Utilize the CDC’s Infection Control in Healthcare Personnel: Epidemiology and Control of Selected Infections Transmitted Among Healthcare Personnel and Patients to manage all exposed health care personnel. 
  • Health care exposures are defined as spending any amount of time while not wearing recommended respiratory protection:
    • In a shared air space with an infectious measles patient at the same time.
    • In a shared air space vacated by an infectious measles patient for up to two hours.
• Reference the CDC’s Be Ready for Measles Toolkit for sample exposure notification and line-listing templates.

For more details on managing measles cases, reporting, testing, and infection prevention and control see the Measles Reporting and Infection and Prevention Control Measures sent on March 27, 2025.

For questions and assistance on preparing for measles cases in your facility, contact the Healthcare Associated Infections (HAI) Prevention Program at DHSWIHAIPreventionProgram@dhs.wisconsin.gov.

Information on measles cases in Wisconsin will be updated weekly on the DHS measles dashboard. Outbreak information will be updated on the Outbreaks, Recalls, and Investigations webpage.

Please do not reply directly to this email message. If you have a question, please email the dhsdphbcd@dhs.wisconsin.gov.