Columbus, Ohio – Concerns are mounting as highly pathogenic avian influenza (H5N1) continues to spread among US dairy cows, causing unease among researchers worldwide. Experts are troubled by the lack of transparency surrounding the outbreak, with many urging for more information to be shared from the federal investigation.
Since the outbreak, 32 herds in eight states have been affected, including Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio, South Dakota, and Texas. The movement of cattle between herds has been cited as a potential factor in the spread of the virus. However, it remains unclear whether all herds are connected in a single outbreak chain or if there have been multiple instances of virus spillover.
The spread of the virus through cattle movements suggests cow-to-cow transmission, although the exact method of transmission remains unknown. The USDA speculates that contaminated milking equipment may be a possible route of transmission since even symptomatic cows exhibit few respiratory symptoms.
Furthermore, reports have surfaced indicating that infected dairy herds in North Carolina showed no visible symptoms of the virus, raising concerns about the silent spread of H5N1 in asymptomatic herds. The uncertainty surrounding the virus’s spread has prompted the USDA to encourage testing for H5N1 in herds showing clinical symptoms or silently spreading the virus.
International experts are closely monitoring the situation, fearing that the outbreak in dairy cows could potentially spread to nearby pig farms. The concern stems from pigs’ ability to be infected with both bird flu and human flu viruses, posing a risk for the emergence of new recombinant flu strains.
To address criticism, the USDA recently released 239 genetic sequences to GISAID, aiming to provide more transparency and access to vital information for the scientific community. Despite the ongoing investigation, the USDA and CDC continue to assess the risk to the public as low, emphasizing the importance of precautions for farmworkers and individuals in direct contact with infected animals.
While H5N1 is deadly to birds, it poses a relatively mild threat to cows and is unlikely to cause deaths. The FDA remains confident in the safety of the milk supply, noting that pasteurization effectively kills the virus. Despite reassurances, experts have called for additional data to confirm the virus’s inactivation during pasteurization.