Dairy worker in California tests positive for H5N1 bird flu

A worker at a dairy cattle facility in California has tested positive for H5N1 bird flu, making it the first case in the state, according to local health officials. The worker had only minor symptoms and the risk to the public is believed to be low.

The individual is a worker at a Central Valley dairy facility experiencing an outbreak of bird flu, according to the California Department of Public Health (CDPH). The individual, whose age and sex were not disclosed, reported conjunctivitis (eye redness) as the only symptom.

“Once the local health department was notified, their public health laboratory tested the individual for H5N1, and CDPH was notified of a ‘presumptive positive’ result,” the department said in a statement on Thursday. Specimens were forwarded to the CDC for official confirmation.

“Ongoing health checks of individuals who interact with potentially infected animals helped us quickly detect and respond to this possible human case,” said Dr. Tomás J. Aragón, the state’s public health officer. “We want to emphasize that the risk to the general public is low, and people who interact with potentially infected animals should take prevention measures.”

Health officials say the risk to the general public remains low but people who interact with infected animals, particularly dairy or poultry farm workers, are at higher risk of being infected with bird flu. Those workers are advised to use personal protective equipment, or PPE, such as N95 masks, eye protection and gloves.

Pasteurized milk and dairy products continue to be safe to consume, as pasteurization is fully effective at inactivating the bird flu virus, according to CDPH. As an added precaution, and according to longstanding state and federal requirements, milk from sick cows is not permitted in the public milk supply.

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

A newer strain of H5N1, clade 2.3.4.4b, has raised concern due to its global spread and the growing number of cases in mammals, including outbreaks among dairy cows in the U.S. Only a limited number of human cases have been reported so far after contact with infected birds or cows.

Earlier this week, officials confirmed that H5N1 bird flu has so far been found at 44 dairies across California, the nation’s largest producer of dairy.

Twenty-eight human cases of H5N1 bird flu have been reported so far this year, including 15 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 one each in Texas, California and Missouri – were caused by the newer variant, clade 2.3.4.4b.

Last month, a patient in Missouri tested positive for H5N1 bird flu despite having no known links to infected animals. The patient was hospitalized but has since recovered. The source of the infection is unknown but no other cases were reported.