In early 2025, U.S. agricultural authorities confirmed the presence of a new genotype (D1.1) of highly pathogenic avian influenza A (H5N1) virus in dairy cattle in Nevada, distinct from the previously

UNESPECTED ILLNES

In early 2025, U.S. agricultural authorities confirmed the presence of a new genotype (D1.1) of highly pathogenic avian influenza A (H5N1) virus in dairy cattle in Nevada, distinct from the previously dominant B3.13 strain. Successful Farming+2CBS News+2 This second spillover event suggests that wild birds have transmitted the virus to cattle more than once. euronews Infected cows exhibited respiratory symptoms such as coughing and sneezing, along with reductions in milk production. CBS News The novel D1.1 strain has also been linked to a human infection: a dairy worker in Nevada developed conjunctivitis but recovered fully, with no evidence of onward transmission to other individuals. CDC+2WSLS+2 Genetic analysis revealed that the D1.1 virus isolated from the human case harbored a PB2 E627K mutation, previously associated with enhanced replication in mammalian cells. CDC+1 Meanwhile, environmental testing demonstrated that H5N1 remains relatively stable in raw milk, wastewater, and on surfaces, highlighting potential transmission risks via contaminated milk or dairy equipment. CDC In response, the USDA has expanded surveillance through its National Milk Testing Strategy, and authorities emphasize that, although public risk remains low, individuals with occupational exposure to dairy cattle should maintain strict biosecurity measures. APHIS

Common symptoms

Reduced milk production: A sudden and significant decrease in the amount of milk being produced is a key indicator.

Changes in milk: Milk may appear thickened, clotted, or colostrum-like.

Loss of appetite: Cows may eat less than usual.

Lethargy: Affected animals may seem tired or unusually sluggish.

Fever: A low-grade fever is a common symptom.

Digestive issues: Some cows may have tacky stools or diarrhea.

Other potential symptoms

Reproductive problems: Abortions in mid-to-late pregnancy have been anecdotally reported.

No symptoms: Some infected cows may not exhibit any signs of illness.

Effects on humanity

Transmission risk: The primary risk for human infection is direct contact with infected or potentially infected cattle, such as dairy cows.

Exposure to fluids: Exposure to bodily fluids like saliva, milk, and feces can lead to infection.

Symptoms: Symptoms can range from mild (like conjunctivitis or flu-like symptoms) to severe (acute respiratory illness). Severe complications can include pneumonia, sepsis, and respiratory failure.

Treatment for humans: While no specific cure exists for the virus itself, supportive care is used to manage symptoms.

Food safety: Commercial milk is safe to drink because pasteurization effectively inactivates the H5N1 virus. However, unpasteurized milk from infected herds is a health hazard.

Curing and prevention

For humans: There is no single cure, and treatment focuses on managing symptoms. Antiviral drugs that are used for seasonal flu may be considered, but their effectiveness can vary.

Preventing infection: The best prevention is to avoid direct contact with infected animals. People who work with cattle or other animals should take precautions, including:

Wearing personal protective equipment (PPE) like gloves, masks, and eye protection.

Avoiding contact with sick or dead animals.

Washing hands frequently, especially before eating.

Laundering outer clothing after working with potentially infected animals.

ReferencesCenters for Disease Control and Prevention. (2025, February 26). A(H5N1) bird flu response update. CDC. CDCCenters for Disease Control and Prevention. (2025, July 7). Current situation: Bird flu in dairy cows. CDC. CDCCrawford, F., Yinda, K. C., Mukesh, R. K., Ochwoto, M., Gallogly, S., Wickenhagen, A., … de Wit, E. (2025). Highly pathogenic avian influenza A(H5N1) virus stability in irradiated raw milk and wastewater and on surfaces, United States. Emerging Infectious Diseases, 31(4). CDCEuronews. (2025, February 6). Bird flu: US detects new type of H5N1 virus in dairy cows. Euronews. euronewsKaiser, F., Cárdenas, S., Morris, D., Lloyd-Smith, J. O., Bibby, K., & Munster, V. J. (2025). see above CDC article.PBS News / Associated Press. (2025, February 6). A different version of bird flu detected in dairy cows in Nevada. PBS News. PBSUSDA / Animal and Plant Health Inspection Service. (2025). Epidemiological bulletin: 2024 highly pathogenic avian influenza (H5N1) – livestock event, Nevada and Arizona dairy investigation. APHISWashington Post. (2025, February 10). New version of bird flu infects Nevada dairy worker. The Washington Post. The Washington Post