The US Centers for Disease Control and Prevention (CDC) has confirmed the first US case of avian influenza (bird flu) in a human who was not exposed to sick or infected animals.

The case was reported in the state of Missouri after being identified through a seasonal flu surveillance system.

The patient, who was hospitalised, had underlying medical conditions, was treated with influenza antiviral medications, subsequently discharged, and has recovered.

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Following initial test results on a sample from the patient, a specimen was forwarded to CDC for further analysis which confirmed the presence of bird flu September 6.

The CDC said that it has not identified any transmission of the virus among the patient’s close contacts or any other person.

An investigation into the potential exposure is ongoing by the Missouri Department of Health and Senior Services (DHSS).

This is the 14th confirmed human case of bird flu reported in the US during 2024 and the first case without a known occupational exposure to sick or infected animals.

Outbreaks of bird flu in cattle have not been reported in Missouri, but cases have been reported in commercial and backyard poultry flocks this year.

While other novel flu cases have been detected through the country’s national flu surveillance system, this is the first time that system has detected a case of bird flu.

The CDC said that it 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.

Based on available data, the CDC’s current assessment is that the risk to the general public from bird flu remains low.

The centre said that the results of this investigation will be particularly important in light of the current lack of an obvious animal exposure.

“Findings from the ongoing investigation will inform whether guidance changes are needed,” it said.