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• Posted July 3, 2024

Fourth Dairy Worker Infected With Bird Flu, but CDC Says Public Risk Still Low

Amid an ongoing outbreak of bird flu in dairy cows, a fourth case of H5N1 avian flu has been confirmed in another dairy worker, U.S. health officials reported Wednesday.

The latest case was reported in Colorado, the U.S. Centers for Disease Control and Prevention (CDC) said in a news release.

"As with previous cases, the person is a worker on a dairy farm where cows tested positive for A[H5N1] virus," the CDC said. "The person reported eye symptoms only, received oseltamivir [Tamiflu] treatment, and has recovered."

The first two human bird flu cases -- the first in Texas and a second in Michigan -- also involved only a brief discomfort of the eyes, linked to conjunctivitis, or "pink eye." Both patients recovered.

However, a third case, also reported in Michigan, was the first to present with more typical respiratory symptoms, the CDC noted in a recent health update. That patient has been treated and has since recovered.

So far, H5N1 has not been easily passed between people, and all four farm workers became infected after prolonged contact with dairy cows.

Despite the fourth case of human bird flu, "this infection does not change CDC’s current H5N1 bird flu human health risk assessment for the U.S. general public, which the agency considers to be low," the CDC said. "However, this development underscores the importance of recommended precautions in people with exposure to infected animals."

Infectious disease experts worldwide have been alarmed that an influenza strain previously confined to birds has now made its way into mammals such as seals, dolphins, cows and -- as reported recently -- alpacas.

The concern is that a mutation might arise which renders H5N1 easily transmittable among members of another mammalian species -- people.

Right now, the danger seems to be limited to people who have prolonged contact with animals infected with the virus, such as dairy workers.

For these individuals, the CDC recommends they "wear recommended personal protective equipment when interacting with infected or potentially infected animals and monitor their health for 10 days after their most recent exposure."

"People should also avoid unprotected exposures to animal poop, bedding [litter], unpasteurized ['raw'] milk or materials that have been touched by, or close to, birds or other animals with suspected or confirmed A[H5N1] virus," the agency added.

Raw milk is a special concern, because pasteurization kills off the H5N1 virus. One study released recently found high levels of avian flu virus in raw milk, even after refrigeration. 

Still, the the U.S. Food and Drug Administration reported just last week that a new study it conducted found that the flash pasteurization used in the diary industry effectively kills all bird flu virus. That research has not been published in a peer-reviewed journal yet, so the findings should be regarded as preliminary.

More information

To find out more about H5N1 avian flu, head to the World Health Organization.

SOURCE: U.S. Centers for Disease Control and Prevention, news release, July 3, 2024