LOS ANGELES – In an important move, the Centers for Disease Control and Prevention (CDC) released new guidelines urging farms to test workers exposed to bird flu, even if they have no symptoms.

This comes after a CDC study discovered antibodies in several dairy workers, signaling possible avian flu infection in asymptomatic individuals. This guidance, aimed at minimizing the spread of the virus among livestock farmers, highlights the need for closer monitoring and prevention.

CDC expands bird flu testing to farmworkers

Federal health officials recommend increasing bird flu testing for farm workers, even those who show no symptoms, following a study showing dairy workers may be at risk of infection .

The CDC guidelines come after blood tests indicated that 8 of 115 workers surveyed in Michigan and Colorado had antibodies to the H5N1 avian flu virus. Dr. Nirav Shah, senior director of the CDC, emphasized that these actions are intended to protect farmworkers and prevent the virus from mutating as it spreads.

Study highlights potential for spread in agricultural environments

The recent CDC study, which focused on workers in close contact with infected animals, represents the largest assessment of avian flu exposure in the United States since the virus was first detected in dairy cattle earlier this year.

Bill Powers checks his flock of white turkeys, which have been kept under shelter year-round to avoid exposure to avian flu, on his family farm November 14, 2022 in Townsend, Delaware.

Notably, four of the eight workers with antibodies had no symptoms, suggesting that the virus can spread among agricultural workers without causing obvious signs of illness. Experts say this finding prompted the CDC to update its guidelines.

“In the past, we recommended testing only symptomatic workers,” Dr. Gregory Gray, an infectious disease researcher, said in an Associated Press report. “This updated guidance reflects a growing assessment of the risk posed by H5N1.”

High risk factors on farms

The study found that farm workers’ tasks, which often involve handling milk or cleaning milking parlors, are likely to increase their exposure to bird flu.

None of the eight workers with antibodies wore respiratory protection and only a few used eye protection, raising concerns about adequate safety measures.

Researchers also noted that infected cows often have high levels of virus in their milk, an important risk factor for infection.

Concerns about spreading the virus

Experts warn that each new infection, whether animal or human, increases the risk that the virus will adapt in ways that could increase its danger. Angela Rasmussen, a virologist at the University of Saskatchewan, noted that the current response to H5N1 may be inadequate given the virus’s ability to jump between species.

“If this virus continues to spread across different species, there is a risk that it will mutate in ways that could pose even greater risks to humans,” she said.

Barriers to effective monitoring

While the new CDC guidelines call for expanded testing, researchers have highlighted the challenges of effectively implementing them, particularly due to resistance from farm owners and workers.

Some farm owners are reluctant to allow testing, and many workers may not get tested unless symptoms appear. This reluctance, along with logistical barriers, has slowed efforts to contain the virus on farms.

The epidemic spreads to livestock

Since H5N1 was initially detected in dairy cows, the virus has spread to 446 cattle herds across 15 states. Recently, the U.S. Department of Agriculture confirmed avian influenza in a pig on a farm in Oregon, marking the first detection in a pig in the United States.

This expansion into new livestock populations underscores the urgency of the CDC’s updated recommendations and the importance of proactive testing and preventative measures in high-risk environments.