Unexpected H5N1 Bird Flu Cases in U.S. Cattle and Humans

The recent detection of H5N1 bird flu in U.S. dairy cattle, with at least one human infection reported in Texas through contact with these cows, has surprised influenza researchers. This marks the first noted occurrence of such transmission to cows with this strain, challenging previous assumptions. Currently, cows from 12 herds across five states have tested positive for the virus. The discovery prompts a reevaluation of the potential for bovine infection, which has been historically overlooked in this context despite past indications that such cross-species transmission could occur.

Experts suggest the virus may have reached cattle through contaminated water or grass, influenced by the widespread infection among wild birds, expanding the list of susceptible species. While there’s no evidence yet of beef cattle being affected, vigilance is advised. The Centers for Disease Control and Prevention (CDC) has analyzed the virus from the infected individual, finding it closely related to existing vaccine strains and showing no signs of resistance to flu antivirals. Although infected cows can shed the virus in their milk, risks to the food chain are deemed low due to safety protocols, including pasteurization. The situation raises concerns about the potential for broader transmission among mammals, including the risk of adaptations that could facilitate spread to and among humans, underlining the importance of monitoring and preventive measures.

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[Source: STAT, April 3rd, 2024]