Researchers Discover Extremely Low H5N1 Dose Can Infect Dairy Cattle

A new study has found that as few as 10 particles of the H5N1 avian influenza virus are enough to infect dairy cows, highlighting the challenges of controlling the disease in livestock.

Researchers reported that the virus appears to target the mammary glands rather than the respiratory system, causing infected cows to produce milk with high levels of the virus for more than a week. The findings were published in the journal *Nature Communications*.

Scientists also tested several possible transmission routes, including contaminated milking equipment, feeding calves with infected milk and airborne exposure, but found no clear evidence explaining how the virus spreads between cows.

Experts say more research is needed to understand transmission patterns and develop effective measures to prevent future outbreaks. Since 2024, more than one thousand H5N1 outbreaks have been confirmed in dairy herds across the United States.