The persistent threat of high pathogenicity avian influenza (HPAI) continues to demand urgent international attention as the virus extends beyond avian populations, increasingly affecting mammals. The World Organisation for Animal Health (WOAH) recently highlighted alarming cases of HPAI circulating in dairy cattle in the United States, underscoring its evolving risk to livestock, wildlife, and public health.
While traditionally impacting domestic and wild birds, HPAI has now been detected in over 30 mammalian species, both terrestrial and aquatic. Data from the World Animal Health Information System (WAHIS) reveals that cases typically surge in the Northern Hemisphere from October through February. This cross-species transmission raises significant concerns about the virus’s adaptability and its potential to spill over into new hosts, including humans.
Rising Concerns in Dairy Cattle
Infected dairy cattle in the U.S. have exhibited mild, nonspecific symptoms such as reduced milk production, lethargy, fever, and dehydration. The circulation of the H5N1 strain in cattle is particularly concerning, as it could increase the virus’s adaptation to mammals. Investigations indicate that raw milk from infected cows is a high-risk material, with evidence of horizontal transmission to other cows, cats, and poultry. WOAH advises that only pasteurized or adequately processed milk should be commercialized to mitigate the risk.
Although no specific adaptation of the virus to humans or mammals has been identified, studies are ongoing to explore its transmission dynamics and pathogenicity among cattle and other species.
Preventive Measures and Recommendations
WOAH, in collaboration with FAO, WHO, and its global networks, is closely monitoring the situation. Although the risk to humans remains low for the general population, it is considered moderate for those exposed to infected animals or contaminated environments. Transparency and timely reporting are critical to understanding the disease’s trajectory and avoiding misinformation.
WOAH urges its 183 Member countries to take the following actions:
- Enhanced Surveillance
- Increase monitoring of avian influenza in domestic and wild birds.
- Expand early detection efforts in cattle populations, particularly in regions where HPAI is active.
- Diagnosis and Reporting
- Include HPAI as a differential diagnosis for non-avian species exhibiting symptoms.
- Report all cases of HPAI in unusual hosts, such as cattle, through WAHIS and share genetic sequences of the virus in public databases.
- Preventive Measures
- Apply movement restrictions on infected livestock.
- Enforce biosecurity measures in farms, especially in milking areas.
- Ensure raw milk from infected cows is not used for animal or human consumption.
- Human Safety
- Protect individuals handling infected livestock by using personal protective equipment (PPE).
- Prevent cross-contamination by limiting access to other livestock facilities post-exposure.
Global Trade Considerations
WOAH emphasizes that trade restrictions on healthy cattle and their products should only be imposed based on a scientifically justified risk analysis. Import measures must align with WOAH’s Terrestrial Animal Health Code. Technical guidelines for diagnostic testing of Influenza A in cattle and other species, including milk and nasal swab sampling, are available on the OFFLU website and are regularly updated.
By prioritizing surveillance, biosecurity, and informed decision-making, the global community can work together to mitigate the risks posed by this evolving threat.
