JAMA: Vigilance Urged Against Bird Flu Amid Ongoing Outbreaks in Mammals

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This spring, Runstadler and colleagues published a study in Emerging Infectious Diseases reporting H5N1 virus spillover into New England harbor and gray seals found stranded off the coast of Maine in June and July of 2022. The data did not support seal-to-seal transmission as the main route of infection, and Runstadler and his coauthors concluded that the seals were likely infected “through environmental transmission of shed virus.”

More recently, Peru reported nearly 3500 dead sea lions affected by avian influenza off the country’s coast this March. And in May, Chile reported the deaths of 9420 marine mammals infected with the virus, including more than 8000 sea lions and more than 1000 Humboldt penguins.

“For the most part, I think this is still bird to mammal [transmission], but it is very difficult to discern in the short-term,” Runstadler wrote in his email. “The number of different marine mammal infections is cause for concern,” he added, “and certainly if we detected sustained die-off or transmission in these hosts, it would be of greater concern.”