That human case of A(H5) avian flu in Missouri that had no known contact with poultry or other animals has been confirmed by the U.S. Centers for Disease Control and Prevention.
The Missouri Department of Health and Senior Services (MDHSS) detected this most recent human case of avian influenza through the state’s seasonal flu surveillance program.
The CDC confirmed the findings after a sample from the Missouri patient was sent for confirmatory testing.
The testing found the patient, who was hospitalized, had underlying medical conditions but had no immediate known exposure to animals.
The patient was treated with influenza antiviral medications in the hospital, then discharged, and has since recovered.
The Missouri case is the 14th human infection with the H5 virus in the United States in 2024. In every other case, the patient had contact with a poultry flock or dairy cattle herd, where the presence of the H5N1 virus was confirmed.
Other human cases of avian influenza have been confirmed in Colorado, Texas, and Michigan.
While other novel flu cases have been detected through the country’s national flu surveillance system, this is the first time the system has detected a case of H5N1.
Targeted H5N1-outbreak-specific surveillance has been conducted as part of ongoing animal outbreaks and has identified all the other cases. In this case, the patient’s specimen initially tested positive for flu A but negative for seasonal flu A virus subtypes. That finding triggers additional testing.
The CDC closely monitors available data from influenza surveillance systems, particularly in affected states. There hasn’t been any sign of unusual influenza activity in people, including in Missouri.
Based on available data, the CDC’s current assessment is that the risk to the general public from H5N1 remains low. The CDC’s recommendations related to the H5N1 virus have not changed at this time. As always, circumstances may change quickly as more information is learned.
The results of the Missouri investigation will be particularly important given the current lack of obvious animal exposure. While rare, novel influenza A cases have been reported where an animal source cannot be identified.
CDC’s primary concern in these situations is that no onward transmission occurs. Findings from the ongoing investigation will inform whether guidance changes are needed.
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