Significant increase in influenza activity in Missouri, City of St. Louis

The City of St. Louis Department of Health has recently observed a significant spike in the number of influenza cases reported in the state.

In Week 52, ending Dec. 27, 2025, the City of St. Louis reported its highest weekly percentage of the current season for ILI visits in emergency departments. Case counts have been consistently increasing over the past month, with a significant increase in the last week of 2025. *Note: ILI is influenza-like illness.

Influenza A accounts for 97% of reported cases with adults aged 25 to 49 logging the highest number of cases for both week 52 and in total.

The purpose of this Department of Health Advisory is to urge health care providers to advise patients on ways they can prevent illness and to receive a vaccine if they are able to do so and have not. This information should be shared widely with the public in an attempt to stop the spread of Influenza A and B.

Those most at-risk include people 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), people with a body mass index (BMI) of 40 kg/m2 or higher, pregnant women, and children younger than 5 years.

Ways to prevent Influenza infection:

Get a flu vaccine.

Annual flu vaccines are recommended for all persons aged 6 months and older who are not at risk for complications.