Researchers at the University of Pittsburgh School of Public Health have identified that H5N1 bird flu infects dairy cattle primarily through specific N-linked sialic acid receptors found in mammary glands, rather than the respiratory tract. This discovery explains why the virus causes severe mastitis in cows instead of traditional respiratory symptoms, providing a new framework for predicting how the virus may adapt to different host species.
Why does H5N1 affect cow udders instead of lungs?
The virus bypasses the respiratory system in cattle because of the specific distribution of glycan receptors. According to a study published in Science Advances, while flu-related receptors exist in the noses and lungs of cows, they do not function in the “lock-and-key” manner required for H5N1 to bind. Instead, N-linked sialic acid receptors are pervasive in the mammary tissue. Lead author Suresh Kuchipudi, Ph.D., notes that these udders act as a “perfect breeding ground for the virus,” causing severe, necrotizing mastitis that initially caught veterinarians off guard because they were searching for common bacterial pathogens.
Before this discovery, many experts assumed H5N1 would follow the same respiratory infection patterns seen in other mammals. The shift in tissue tropism—from lungs to mammary glands—demonstrates how a virus can evolve to exploit unique physiological features of a new host species.
How can scientists predict future viral jumps?
The research team utilized a “multimodal approach” to map the detailed architecture of host cells. By combining binding experiments, staining methods, and ultra-high-resolution imaging, experts can now preemptively screen different species and tissues for susceptibility. This methodology allows public health officials to determine if a virus might trigger respiratory issues, inflammation, or neurological disease in other animals. By understanding the underlying receptor biology, scientists move from reactive observation to proactive surveillance, potentially saving critical time during future outbreaks.
What are the risks to humans and pets?
The concentration of the virus in raw milk poses a clear occupational risk for farm workers. Because infected cattle shed high viral loads into their milk, experts warn against the consumption of unpasteurized dairy products. According to Dr. Kuchipudi, pasteurization remains highly effective at neutralizing the virus. Previous observations of cats dying after consuming raw milk from infected herds further underscore the danger of raw dairy consumption for both domestic animals and humans.
Always verify that dairy products are pasteurized. The heat process used in commercial pasteurization effectively destroys the influenza virus, rendering the milk safe for consumption.
Frequently Asked Questions
- Why were veterinarians surprised by the H5N1 outbreak in cows?
Veterinarians were looking for respiratory symptoms typical of influenza in other mammals. Because the cows presented with mastitis, the initial focus was on bacterial pathogens. - Is pasteurized milk safe to drink?
Yes. According to researchers at Pitt Public Health, pasteurization is effective at killing the H5N1 virus. - Can this research prevent future pandemics?
While it cannot prevent every jump, the framework helps scientists screen species and tissues for susceptibility, allowing for faster, more targeted public health interventions.
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