A recent Morbidity and Mortality Weekly Report by the Centers for Disease Control (CDC) showed some dairy workers in Michigan and Colorado exposed to highly pathogenic avian influenza (HPAI) A(H5) were asymptomatic or mildly ill. The study comes as more human cases were reported in a child in California and a poultry worker in Oregon.
From June to August, the CDC worked with health departments in Michigan and Colorado to study HPAI virus exposure among dairy workers. Eight of 115 workers tested had antibodies indicating recent infection, with all reporting tasks like milking cows or cleaning milking parlors. CDC found four workers recalled being ill when cows were infected. Still, the other half of the workers with antibodies reported no illness, underscoring the challenge of detecting asymptomatic or mild cases.
In interviews with dairy workers, CDC noted they performed various tasks such as cleaning manure (62%), milking cows (59%) and moving cattle (49%), which could expose them to the virus. Despite these risks, only 37% used eye protection and 21% wore respirators, falling short of CDC recommendations. None of the workers with confirmed infections used recommended personal protective equipment (PPE) when handling infected animals.
CDC suggested these findings highlight the need for ongoing worker health monitoring, as asymptomatic or mild cases could go undetected without active screening. The agency also suggested that improving PPE usage, particularly for high-risk activities like cleaning milking parlors, is essential to protecting workers from exposure. CDC also stressed the need for education and outreach, especially for Spanish-speaking workers, who comprised most of the study participants. The agency further suggested expanding herd testing and educating workers about PPE use, reducing transmission risks and ensuring worker safety and public health.
More human cases
A child in Alameda County, CA, tested positive for bird flu after experiencing mild respiratory symptoms, though no contact with infected animals has been reported. Public health experts are investigating possible exposure to wild birds. The California Department of Public Health (CDPH) reported the child was recovering at home and poses little risk of spreading the virus, as the positive test showed low-level detection. Follow-up testing four days later was negative, and additional tests revealed the presence of common respiratory viruses that likely caused the symptoms.
CDPH, in collaboration with local health officials and the CDC, is further investigating the case. Test specimens have been sent to the CDC for confirmatory testing. All close family members tested negative for bird flu and were found to have the same common respiratory viruses as the child. Family members are receiving preventive treatment as a precaution, and no evidence of person-to-person spread has been detected.
The CDC confirmed a human case of bird flu connected to an outbreak at a Clackamas County, OR, commercial poultry operation that affected thousands of birds. Public health officials have not disclosed details about the individual or the operation. According to the CDC, there is no evidence of person-to-person transmission, and the risk to the general public remains low.
Dr. Dean Sidelinger, Oregon’s state epidemiologist, emphasized that those at the highest risk of infection are individuals with close or prolonged exposure to infected birds or contaminated environments. Oregon Health Authority epidemiologists are collaborating with local public health officials, the Oregon Department of Agriculture and the CDC to monitor exposed individuals and respond promptly if any new symptoms arise. — Charles Wallace, WLJ contributing editor
