As people worry about the impending threat of COVID-19 and monkeypox, seals in the Northeastern United States may have another virus to worry about: bird flu. The marine mammals came down this summer with a new H5N1 strain thought to have crossed over to them from birds.
The disease has led to a population-scale outbreak that has resulted in the largest mammalian death caused by the new avian influenza virus, suggesting that even marine life can be affected by diseases affecting terrestrial animals. Researchers from the Cummings School of Veterinary Medicine at Tufts University detail the outbreak in a new report form.
Although scientists hoped that last spring’s H5N1 outbreak would mimic the December 2014 outbreak, which nearly disappeared in six months, this latest spread continued to rage through the summer. This outburst, after a kind Article published in August 2022 has swept across the US, causing nearly 400,000 wild bird deaths and causing massive damage to domestic poultry farming.
As outbreaks continued to escalate over the past year, concerns have been raised about the potential impact on birds migrating south for the winter. However, one of the biggest concerns about the recent outbreak is the spread of bird flu to marine mammals. The first wave of H5N1 infections peaked in March 2022 and mostly affected raptors; The second wave started in gulls in June and marked the spread to marine mammals, particularly seals. The preprint hypothesizes that the infections in seals may have been linked to ecological interactions between seals and birds. Avian flu may also have spread to seals through dead birds, bird droppings, or infection from seal to seal.
While mammals have typically been viewed as cul-de-sac hosts, not further spreading the infection, the preprint reports stated “it is currently unclear whether marine mammal spillover will also be a dead-end transmission event” based on the larger scale of new infections. The spread of H5N1 via wild birds, and now seals, cannot be controlled as they are highly mobile populations, leading to the potential future emergence of new strains of the virus that can threaten other mammals, including humans. Given the potential threat of zoonotic spillover, where diseases spread from wildlife to humans, the scientific community remains vigilant about emerging viruses that are difficult to predict and control.