The recent discovery of bird flu virus in dairy cow milk has shed light on a new target for the H5N1 virus – the mammary glands. A study conducted by virologist Amie Eisfeld and her team at the University of Wisconsin-Madison found that the virus can spread to the mammary glands of mice and ferrets when exposed directly to their noses.
This new finding suggests that mammary infections may not be unique to cows, as previously thought. The H5N1 virus, which is currently circulating in U.S. cows and has caused outbreaks in more than 135 dairy herds in 12 states, has been detected in cow milk. The virus exploits a ducklike protein on the surface of cows’ mammary cells to gain entry, potentially explaining how it spreads among cattle.
Despite being detected in cows’ respiratory tracts, there is little evidence of respiratory transmission of the virus among cows. The study found that infected female mice could transmit the virus to their pups through milk, but no transmission occurred through direct contact. This suggests that the virus is not very efficient at spreading through the air.
While the overall risk of bird flu transmission to humans remains low, farm workers in direct contact with infected animals are at a higher risk. So far, four people in the United States have developed mild cases of bird flu after working with infected animals. Public health officials advise against consuming raw milk, but pasteurized milk on grocery store shelves is safe to consume as the pasteurization process effectively kills all H5N1 virus in milk.
Researchers are closely monitoring the virus to see if it is adapting in ways that could increase the risk of spread. Cows have entry portals for both human and bird flu viruses, which could potentially allow for the exchange of genes between the two viruses. This gene swapping could lead to the emergence of new influenza strains that are more adept at infecting humans.
This study highlights the importance of continued surveillance and research on bird flu viruses to better understand their transmission and potential risks to both animals and humans. By studying how the virus interacts with different tissues and hosts, scientists can gain valuable insights into how to prevent and control future outbreaks.
