The number of human cases of H5N1 bird flu in the U.S. this year has risen to 14, with the latest one marking the first detected in a person who is not a farmworker.
The Centers for Disease Control and Prevention (CDC) confirmed on Friday that a person with no known exposure to infected animals had tested positive for the avian flu in a hospital, prompting the Missouri Department of Health and Senior Services (DHSS) to launch an ongoing investigation into how the virus was transmitted.
The patient, an adult whose name was not released over privacy concerns, had underlying medical conditions and recovered from the virus after being treated with antiviral medications, according to Missouri DHSS. They have since been released from the hospital, with no infections having been detected among their close contacts.
In addition to being the first case not linked to contact with a sick animal, Missouri officials said that the case was the first detected using the state’s flu surveillance system, rather than protocol specifically tailored to detect H5N1 cases related to the recent outbreak in livestock like dairy cows and poultry.
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Newsweek reached out for comment to the CDC via email on Friday night.
A multistate outbreak of the virus emerged among dairy cows in mid-March, with several infections in dairy and poultry workers being detected in the months that followed. The latest infection makes Missouri the fourth U.S. state with a human case this year.
The following map created by Newsweek shows that all of this year’s human H5N1 cases have been limited to Colorado, Texas, Michigan and Missouri:
Newsweek / Flourish
The small number of human cases have been concentrated largely in Colorado, where a total of 10 infections have been detected. Two infections were found in Michigan, while one case was discovered in both Texas and Missouri.
The Missouri patient was hospitalized on August 22, although it is not clear whether they were hospitalized due to the infection or another medical issue. No cases of human-to-human transmission have ever been detected in the U.S.
In humans, bird flu can range in severity from no symptoms to mild symptoms like eye infections or upper respiratory illness. In severe cases, bird flu can cause pneumonia.
“CDC continues to closely monitor available data from influenza surveillance systems, particularly in affected states, and there has been no sign of unusual influenza activity in people, including in Missouri,” a statement from the CDC reads.
“It is important to note that, while rare, there have been novel influenza A cases where an animal source cannot be identified,” it continues. “The main concern in these situations is that no onward transmission is occurring.”
The CDC said that overall risk to the public “remains low” but “guidance changes” might be required depending on the results of an investigation. Attempts to discover more about the infection by sequencing the genome of the virus are underway.
