New 'Seal Flu' Outbreak Could Pose Threat to Humans

Harbor Seals at Woods Hole Science Aquarium.

Over the past few years, bird flu and swine flu outbreaks have harmed wide swaths of global populations—now scientists are warning that a new flu that developed in seals off the New England coast could pose a human threat.

Last winter, officials found 162 dead harbor seals in what was then thought to be a pneumonia outbreak. But a new investigation by Columbia University researchers has found that the dead seals had a new mutation of the influenza A virus. The virus started as avian, or bird flu, but the mutations may have created something new altogether.

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"Once it moves into seals, it becomes seal flu," says Ian Lipkin, director of the Center for Infection & Immunity at Columbia University.

The fact that the virus was transferred from a bird to a mammal and the apparently high mortality rate of the seals that were infected raises concerns for humans, Lipkin says. In the seals, the virus mutated to become more transmissible in mammals, a key component for any human outbreak.

"Whenever you have something like this that emerges in wildlife that's associated with high mortality, we have to consider the possibility it could extend to humans," he says. "70 percent of emerging diseases move from animals to people—there's a long list of those: Ebola, hepatitis C, other flus, HIV, etc."

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According to the Centers for Disease Control, influenza A viruses have been known to infect seals, ducks, chickens, pigs, whales, and horses, but such a large outbreak is extremely rare, Lipkin says.

Last winter, at least 12 Americans were infected with a new swine flu strain called H3N2v in five states, and humans are obviously much more likely to come into contact with a domesticated pig than a wild seal. But it only takes a few humans to be infected with a particularly virulent flu strain to start spreading the virus, Lipkin says.

"This may in fact be a new route in [to human infection]," he says. "I can't tell you if it'll move into humans, but it has the potential to do so."

Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at jkoebler@usnews.com.

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