Bird Flu Outbreak Expands: H5N1 Variant Detected in U.S. Dairy Cattle

A new strain of the H5N1 avian influenza virus has been detected in dairy cattle across multiple U.S. states, marking a significant development in the ongoing outbreak. This spillover event raises concerns for dairy farmers and public health officials due to potential impacts on milk production, farm operations, and worker safety.

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Key Developments

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• Detection in Dairy Cattle: The USDA confirmed that the D1.1 genotype of H5N1, previously  found in wild birds and poultry, has now infected dairy herds in Nevada and other states¹.  This is the first time this particular strain has been detected in cattle². 
• Spread and Surveillance: The National Milk Testing Strategy has enrolled 36 states,  covering two-thirds of U.S. dairy herds². Recent detections were made through bulk milk  testing in Nevada³. 
• Human Cases: The CDC reports nearly 70 human cases, primarily among dairy workers  exposed to infected cattle⁴. Symptoms have been mild, with no evidence of human-to human transmission⁵.

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Impact on Dairy Farmers

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• Milk Production Declines: Infected cows are showing reduced appetite, lethargy, and a 10– 20% drop in milk production over 7–10 days⁶. 
• Economic Costs: Farmers face increased costs for biosecurity measures and potential  losses from milk supply disruptions⁶. 
• Health Risks: Experts warn against consuming raw milk, as it may carry the virus⁷.

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Recommendations for Dairy Farmers

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• Strengthen Biosecurity: Isolate new animals for at least 30 days, sanitize shared  equipment, and limit personnel movement between farms⁸. 
• Monitor Herds: Conduct regular testing and isolate symptomatic animals immediately³. 
• Stay Informed: Follow USDA and CDC updates on policy changes and financial assistance  programs related to H5N1 management².

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What’s Next?

Researchers are closely monitoring the D1.1 genotype to assess its potential risks to livestock and humans. While the CDC maintains that the overall risk to public health remains low, continued vigilance is essential to prevent further spread³.