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Missouri reports human bird flu case with no link to animals

Published on

September 6, 2024

Micrograph of avian influenza viruses, also known as bird flu (Credit: CDC/F.A. Murphy)

A patient in Missouri has tested positive for H5 bird flu, but unlike previous cases there is no known link to animals, according to state and federal officials. The source of the infection is still unknown.

The patient, who was only described as an adult with underlying medical conditions, was hospitalized on August 22. After testing positive for Influenza A, a specimen was sent to the state lab for additional testing, which revealed the H5 subtype.

“The specimen was forwarded to CDC for additional testing and was confirmed as H5 subtype of flu, also known as a bird flu, or avian flu. Additional virus characterization is underway at CDC,” the Missouri Department of Health said in a statement on Friday.

The patient has since recovered, was released from the hospital and so far there is no indication of ongoing transmission among close contacts, according to the CDC.

Unlike previous human cases of bird flu in the U.S., there is currently no indication about the possible source of the infection as the patient reported no recent exposure to animals. This is also the first time a case has been found through the influenza surveillance system.

“Based on available data, CDC’s current assessment is that the risk to the general public from H5N1 remains low,” the agency said in a statement. “As always, circumstances may change quickly as more information is learned. The results of this investigation will be particularly important in light of the current lack of an obvious animal exposure.”

The statement added: “The main concern in these situations is that no onward transmission is occurring. Findings from the ongoing investigation will inform whether guidance changes are needed.”

While the exact type of H5 bird flu has not yet been determined, it is likely H5N1, and possibly clade 2.3.4.4b, which has raised concern due to its global spread and the growing number of cases in mammals, including an outbreak among dairy cows in the U.S.

LINK: A list of all human cases of H5N1 bird flu since 2021

Twenty-six human cases of H5N1 bird flu have been reported so far this year, including 13 in the U.S., 10 in Cambodia and one each in Australia, Vietnam and China. Only the U.S. cases – 10 in Colorado, 2 in Michigan and 1 in Texas – were caused by the newer variant, clade 2.3.4.4b. All were linked to animals.