A new strain of bird flu you should be worried about? Maybe: In New England last fall, 162 harbor seal pups were killed by H3N8, a flu subtype that has crossed over from birds to dogs and horses in the past. Other strains of flu have previously crossed over from birds to seals, but this incident is particularly troublesome because never before has a strain been able to pass from seal to seal. Scientists are now studying H3N8 and its potential threat to humans, the New York Times reports.
While bird flu viruses have been known to infect mammals, they typically do not then spread from mammal to mammal, which is why strains like H5N1 are so worrisome. A virus that spreads in seals is even more concerning, because seals—like pigs—can carry both bird flu and mammal flu simultaneously, thus ultimately producing new, hybrid strains. Scientists are concerned, but caution that the severity of the threat is yet unknown. "If it adapts better to mammal hosts, it may well start to move into humans," says one. "This is clearly a virus for which we need some surveillance."