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Mutated Flu Virus Kills New England Seal Pups


Harbor seal pup.Harbor seal pup. Source:

When more than 162 young harbor seals were discovered stranded or dead on New England beaches in the fall of 2011, it was officially declared by the federal government as an Unusual Mortality Event (UME). For marine mammals, a UME is a stranding that is unexpected, involves a significant die-off of the population, and demands an immediate response.

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The National Oceanic and Atmospheric Administration (NOAA) assembled a team of scientists to investigate. Wildlife experts from the USGS National Wildlife Health Center contributed their expertise by isolating the virus from the tissues of the seals. They were able to characterize the virus as a type of influenza virus most closely related to the avian influenza H3N8 viruses commonly found in wild birds.

Collectively, the team of scientists determined that the H3N8 seal virus is likely to have caused the 2011 mortality event in New England.  Further, it may pose a continued threat to marine mammals on the nation’s coast.  Dr. Hon Ip, a USGS virologist at the National Wildlife Health Center, said, “What was surprising was that the seal virus contained genetic changes that have been shown to increase mammalian infection. Of the influenza viruses that have been previously isolated from seals, none shows this pattern of genetic change toward adapting to mammals.”

Katie Pugliares and Michael O’Neil with the New England Aquarium preparing a harbor seal carcass for necropsy. Photo Credit: New England Aquarium.

Is there a Wildlife-Human Connection?

In the last few years, the highly pathogenic avian influenza H5N1 virus has been shown to cause disease and even death in cats, dogs and people. It is estimated that more than 70 percent of the emerging infectious diseases that can infect people have a wildlife origin. The seal H3N8 virus, and its adaptation to mammals, raises questions about whether this virus may be the latest example of an emerging infectious disease

Future Efforts for a Healthy Marine Ecosystem

While the importance of potential threats to human health and domestic animals from pathogens is of concern, these emerging pathogens are also a potential threat to conservation efforts in regard to maintaining the health of wildlife such as harbor seals and the overall function of a healthy marine ecosystem.

The National Wildlife Health Center is at the forefront of identifying and understanding disease threats to our native wildlife, as well as sharing that information with public health and domestic animal health agencies.  Partnerships, such as this effort with the NOAA investigative team, foster better understanding of the epidemiology and ecology of wildlife disease, provide better information for management decisions, and ultimately help protect the health of all species.

The investigative team from the USGS, Columbia University, NOAA, New England Aquarium, Sea World, and the EcoHealth Alliance recently published its findings on the influenza virus that fatally afflicted the harbor seals in the scientific journal mBio.

Dead harbor seal found in New England in 2011. Photo Credit: New England Aquarium.

More Information

Visit the USGS National Wildlife Health Center homepage.

Learn more about USGS avian influenza research.

Find out what other research the USGS is doing on microbiology.


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