Scientists express concerns about the transmission of bird flu among cattle

Bird flu’s emergence among dairy cattle has scientists on edge as they delve into the complexities of this unexpected spillover. The potential risks to human health depend on the virus’s ability to adapt for better transmission among mammals.

Recent findings offer some relief: Unlike typical respiratory infections in cattle, bird flu doesn’t manifest as such, with affected animals not shedding significant virus amounts through nasal or oral routes. Instead, experts suspect “mechanical transmission” during milking, supported by high virus concentrations in milk.

Thijs Kuiken, from Erasmus University Medical Center, underscores this anomaly, noting the virus’s departure from typical mammalian flu behavior.

However, caution looms as researchers scrutinize genetic clues hinting at evolutionary shifts. The mutation in the PB2 gene, often implicated in mammalian flu adaptation, raises concerns but doesn’t signal immediate human transmission risks. Nichola Hill, of the University of Massachusetts Boston, emphasizes the need for multiple gene mutations for pandemic potential.

Key changes would involve the virus’s binding protein adapting to human upper respiratory receptors, facilitating efficient cell entry and replication. Darwyn Kobasa, at Canada’s National Microbiology Laboratory, explains that stable binding and replication are vital for airborne transmission.

Despite bird flu’s spillover into mammals, particularly cattle, such mutations aren’t yet observed for efficient human spread. Anice Lowen, from Emory University, underscores the complexity, noting unknown factors influencing adaptation.

Infections often trace back to bird contact, posing risks through carcass consumption or fecal exposure. Michelle Wille, at the University of Melbourne, suggests contaminated feed may introduce the virus to cattle.

However, such explanations don’t fully elucidate mass mammalian infections, seen in seal and sea lion die-offs and a Spanish mink farm outbreak. Lab studies on ferrets offer insights, with some showing limited airborne transmission potential.

While informative, ferret experiments require cautious interpretation. Lowen urges restraint, citing limited evidence for natural airborne transmission.

As scientists navigate bird flu’s complexities, ongoing vigilance is crucial. The threat of human transmission remains a concern, prompting continuous monitoring and preemptive measures to curb potential pandemics.

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