The recent case of bird flu infection in a human, only the second in US history, is suspected to be connected to the recent outbreak of avian influenza A(H5N1) among dairy cows.
The current outbreak of highly pathogenic avian influenza (HPAI) began in 2022, primarily with the H5N1 strain. Until recently, this strain had never been detected in ruminants.
However, in late March, the USDA reported that cows affected by a ‘mystery disease’, characterized by producing thick, colostrum-like milk and reduced appetite, were indeed suffering from avian flu. These cases are believed to be associated with wild waterfowl, although federal agencies are exploring various scenarios.
Previously, experts believed cows to be ‘dead-end hosts’, meaning they were unlikely to transmit the virus to other cows or humans. Nevertheless, individuals with close or prolonged unprotected contact with infected animals or environments are considered at higher risk.
First Recorded Human Case of Bird Flu Linked to Exposure to Sick Dairy Cows in the US (Credits: NPR)
The Centers for Disease Control and Prevention (CDC) stated that the individual presumed to be infected with the A(H5N1) strain had been exposed to dairy cattle in Texas, exhibiting only redness in the eyes consistent with conjunctivitis. They are receiving treatment with antiviral flu medication and are recovering while isolating.
The CDC reassured that this infection doesn’t alter the risk assessment of H5N1 bird flu for the general public, which remains low.
Over the weekend, the USDA confirmed a case of HPAI in a Michigan dairy that had recently received cows from Texas. The virus strain found in Michigan closely resembled the one confirmed in Texas and Kansas, indicating that cow-to-cow transmission cannot be ruled out.
Although the USDA is hesitant to impose movement controls, it advises veterinarians and producers to maintain good biosecurity practices, test animals before moving them, minimize animal movements, and isolate sick cattle from the herd.
However, the Nebraska Department of Agriculture (NDA) has implemented restrictions on the importation of dairy cattle due to the HPAI detections. The NDA mandates that all breeding female dairy cattle entering the state obtain a permit before entry, effective for 30 days and subject to reevaluation.
Additional ‘presumptive’ positive test results have been reported by USDA’s National Veterinary Services Laboratories in New Mexico, Idaho, and Texas, suggesting further detections of HPAI.
Federal and state agencies continue testing swabs from sick animals and unpasteurized clinical milk samples, as well as conducting viral genome sequencing to discern any underlying causes for symptoms.
Federal agencies emphasize that commercial milk supplies remain safe for consumption as pasteurization deactivates the virus. Moreover, the unique viscosity of the milk produced by infected cows makes it unlikely to contaminate bulk tanks, according to experts from Penn State. Dairies are required to dispose of milk from ill cows.
Regarding the impact on milk supply, losses from symptomatic cattle have been limited, and any decrease should be offset by spring production increases, according to the USDA.
The CDC maintains that the current risk to human health from the virus is low, but acknowledges the potential for severe disease in infected individuals. Farmers are advised to avoid unprotected contact with sick animals or their waste, while healthcare providers should consider HPAI in patients with respiratory symptoms who may have been exposed to sick animals.
The Texas Department of State Health Services (DSHS) is collaborating with state and federal agencies to investigate human and animal cases, aiming to understand the virus’s spread to protect both livestock and those working with them.
