A Nov. 7 study in Michigan and Colorado found that 7 percent of tested workers had antibodies indicating previous H5N1 infection.
Federal health officials have called for expanded bird flu testing among farmworkers following a study revealing signs of infection in asymptomatic dairy workers.
Dr. Nirav Shah, principal deputy director of the U.S. Centers for Disease Control and Prevention (CDC), told reporters on Nov. 7 that farmworkers who come into close contact with infected animals should be tested and offered treatment even if they are asymptomatic.
“The purpose of these actions is to keep workers safe, to limit the transmission of H5 to humans, and to reduce the possibility of the virus changing,” Shah said.
The new recommendations follow a Nov. 7
study involving 115 farmworkers in Michigan and Colorado, which found that eight of them—or 7 percent—had antibodies indicating previous H5N1 infection. This suggests the virus may have infected more people than the 46
officially recorded U.S. cases as of Thursday, most of which involved exposure to infected dairy cows or poultry.
“Some of the persons who did not report being ill might have experienced only very mild symptoms,” the study reads. “This finding highlights the need to actively monitor exposed workers by assessing the presence of any mild symptoms and provide a safe environment that encourages reporting of even mild illness and allows for rapid treatment with antivirals to prevent progression to severe disease, without risk for repercussions in terms of job security and pay.”
Some workers with HPAI A(H5) antibodies reported illness before infected herds were identified, the study noted. This highlighted the importance of early outreach to dairy workers and swift herd identification through expanded testing and bulk milk monitoring programs.
The study comes alongside findings from a CDC
report on personal protective equipment (PPE) use among dairy farmworkers in Colorado. Even though workers increased PPE use by 28 percent after H5N1 detection on their farms, the use of N95 respirators and other masks remained low, underscoring ongoing challenges in protecting workers.
“Development of messaging by public health agencies that is consistent with CDC PPE
recommendations would help to educate farm owners and workers about the risks associated with caring for ill dairy cows on farms with A(H5N1) detected and could encourage recommended respirator use,“ the study reads. ”Engaging dairy industry representatives and producers to recommend practices limiting worker contact with dairy cattle and their milk, along with PPE use recommendations in high-risk scenarios such as milking, might increase PPE use.”
Human infections with novel influenza A viruses, such as H5N1, occur through exposure to contaminated air, surfaces, or materials,
per the CDC. The agency recommends that employers at high-risk jobs like farming, veterinary care, and food processing implement safety plans, hazard assessments, and controls to protect workers handling infected animals or contaminated materials.
Bird flu symptoms in humans can vary from mild to severe; they include conjunctivitis, flu-like upper respiratory symptoms, fatigue, and shortness of breath. In severe cases, the infection may cause vomiting, seizures, or even death.
The CDC considers the current public health risk from bird flu to be low, but the agency
stated in its latest Nov. 6 situational update that it is “watching the situation carefully” and working with states to monitor people with animal exposures.
