• Multiple measles cases have been confirmed in Missouri and Illinois, with potential exposure at the St. Louis Aquarium, prompting health officials to prepare for a potential outbreak.
• Declining measles vaccination rates among Missouri kindergarteners, especially in certain counties and the city of St. Louis, increase the risk of community spread.
• Health officials are emphasizing the importance of vaccination, combating misinformation, and reactivating the pandemic task force to coordinate preparedness efforts.

Health officials in the St. Louis region are on high alert following the confirmation of measles cases in Missouri and Illinois. A key concern is a potential exposure event at the St. Louis Aquarium on April 30, where an infected individual from Southern Illinois visited, potentially exposing hundreds of visitors. This comes amid a larger multi-state measles outbreak, particularly in Texas, and declining vaccination rates in Missouri, raising fears of a wider outbreak. Officials are urging vaccination and coordinating preparedness measures.

• What: Confirmed measles cases in Missouri and Illinois, including a potential exposure event at the St. Louis Aquarium, leading to increased vigilance and preparedness efforts by health officials.
• Who: Key individuals include Dr. Heidi Miller (Missouri Department of Health and Senior Services), Dr. Mati Hlatshwayo Davis (St. Louis health director), Dr. Alex Garza (head of the pandemic task force), and potentially exposed individuals and school groups. Organizations include the Missouri Department of Health and Senior Services, St. Louis Health Department, and the St. Louis Metropolitan Pandemic Task Force.
• When: The potential exposure at the St. Louis Aquarium occurred on April 30, 2025, between 1-6 p.m. The Missouri Department of Health announced the potential exposure on May 7, 2025. The task force reconvened shortly after.
• Where: The events are centered in St. Louis, Missouri, and Southern Illinois, with broader implications for Missouri and other states due to the multi-state outbreak. The specific location of concern is the St. Louis Aquarium at Union Station.

The confirmed measles cases and potential exposure in St. Louis highlight the ongoing threat of vaccine-preventable diseases. Declining vaccination rates create vulnerabilities, especially in communities with lower immunization levels. The reactivation of the pandemic task force demonstrates a proactive approach, but addressing misinformation and ensuring access to vaccinations are crucial for preventing a widespread outbreak. The situation is further complicated by the infected individual's limited information regarding their movements, hindering contact tracing efforts.

We are, epidemiologically, absolutely at risk for measles. We know when the measles immunization rates dip below 95%, we are absolutely at increased risk. Currently, those numbers are at least 5 points too low. That can make a huge difference.

I do not want us to be in a situation where we drop below herd immunity and start to see some of the levels of really fast transmission that you saw in Texas that did have lower rates of vaccination.

We are working to notify anyone present during the established exposure window. Staff are currently contacting everyone to let them know of exposure and relaying next steps.

The St. Louis region faces a heightened risk of a measles outbreak following confirmed cases and potential exposures. While health officials are taking proactive measures, the success of these efforts depends on increasing vaccination rates, combating misinformation, and effectively tracing potential contacts. The situation remains fluid, and ongoing monitoring and community engagement are essential to prevent a wider outbreak.