Is the H3N8 Flu Found in Harbor Seals In New England a Concern for People?

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Harbor Seals in New England Affected by H3N8 Virus in 2011. Photo credit: I Robinson

In the fall of 2011, more than 150 harbor seals (Phoca vitulina) were found dead on beaches in New England, the majority in northern Massachusetts, New Hampshire and southern Maine.

Katie Pugliares, Senior Scientist and Necropsy Coordinator for the New England Aquarium, spoke with Decoded Science about this Unusual Mortality Event (UME).

UMEs in marine mammals in the US, are declared by the National Oceanic and Atmospheric Administration when there is “a stranding that is unexpected; involves significant die-off of any marine mammal population; and demands an immediate response.”

The 2011 outbreak began in September and continued until December, with the peak occurring in September and October.

Fortunately, as of mid-November 2012, of the eleven cases sent for testing, nine have been negative, with two cases pending.

More significantly, harbor seal mortalities in 2012 have been lower, more in line with previous years. And the seals whose samples were sent for testing did not have the same external lesions as the previous year.

How Does H3N8 Virus Affect Harbor Seals?

Ms Pugliares told Decoded Science that the investigation began early last fall when an unusually high number of young harbor seals in good weight were being found dead on New England beaches. While an increase in the number of recently weaned seals dying in late summer and early fall is normal in wild populations, these animals are generally very thin or even emaciated. In 2011, however, the seals found on New England beaches were not typical ‘failure to thrive’ cases.

In addition, these animals had sores on their mouth and body. Postmortem examinations showed congested, often hemorrhagic, lungs. This is similar to the signs seen in dogs infected with H3N8 in Florida in 2004 and 2005. Other strains of H3N8 found in horses and pigs also tend to cause respiratory disease.

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