A person in Missouri has tested positive for bird flu, reports the US Centers for Disease Control and Prevention (CDC). The patient, who had underlying medical conditions, was hospitalized on August 22 with the condition. This is the 14^th bird flu in humans identified in the United States in 2024. Importantly, it’s the first case to involve no known occupational contact with infected or sick animals. The case comes just a few months after an unprecedented bird flu outbreak among cow herds in the US. 

The patient was treated with antiviral influenza medication. They were subsequently discharged from hospital and made a full recovery. The Missouri Department of Health and Senior Services (DHSS) has opened an investigation into the infection. 

The case was identified through Missouri’s seasonal flu surveillance program. The program flags cases that don’t match any expected seasonal flu virus subtypes for additional testing. The CDC has not identified further transmission of the virus.

H5 bird flu is a type of influenza A virus and is one of five avian flu types known to cause human infection. According to the CDC, H5 bird flu is now widespread in wild birds across the globe and regularly jumps into poultry. It’s mostly in these agricultural settings that the virus has previously infected humans. 

Bird flu strains are classified based on two proteins on their surface. One is called hemagglutinin (H), and the other is neuraminidase (N). Further sequencing is ongoing to determine the neuraminidase status of this latest case of H5 bird flu. H5N1 and H7N9 bird flu have caused most human cases of the disease. H5N1 was first identified in domestic waterfowl in southern China in 1996. The virus infected over 800 people between 2003 and 2016, with a mortality rate of more than 50% - although this may be higher than the true rate, as some mild cases might have gone unnoticed by health authorities. 

The CDC’s current outlook is that the risk of H5N1 to the wider public is low. The CDC’s investigation will prove important to identify how the case arose without an obvious source of transmission from animals. In a statement, the CDC said that this kind of case is not unheard of. “It is important to note that, while rare, there have been novel influenza A cases where an animal source cannot be identified,” they wrote.