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


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Katie Pugliares and Colleague Perform Postmortem Examination on a Harbor Seal. Photo courtesy K. Pugliares, New England Aquarium

What is Known, And Not Known, About H3N8 in Harbor Seals

In 2012, numbers of stranded seals are back to normal and no animals tested thus far have had the H3N8 virus.

This does not necessarily mean the virus is no longer a threat to the wild population.

Between the two major Phocine Distemper Virus (PDV) outbreaks in Europe, which killed 18,00 seals in 1988/1989 and 22,000 in 2002, that virus was not found in European wild populations.

Thus far only young seals, which are at high risk of dying from a variety of factors, appear to have been affected by the H3N8 virus. And these cases represent only a very small proportion of the wild population in the Gulf of Maine, estimated at slightly less than 100,000 animals.

Although it is possible, and even likely, that more seals were affected (surveys were not done on remote beaches, islands or at sea) it is unlikely that the impact on the population was significant.

The finding of the H3N8 virus in this species also sparked concerns for potential transmission to humans. The types of mutations found in this most recent form of the virus are known to increase transmissibility in mammal species. Thus far, however, this H3N8 virus has not been transmitted to people.

Research on the Various Strains of Influenza Virus, including H3N8, is Ongoing. Photo Credit: Centers for Disease Control and Prevention

The lack of cases involving adult animals suggests that there may be some immunity within the general population. This is in contrast to the seal distemper virus in Europe where the adult population was heavily impacted.

It is always advisable to avoid direct contact with wild animals as injuries, including bite wounds, are a risk, and disease transmission is a concern in both directions.  Any species runs a higher risk of disease when exposed to pathogens that the body has not encountered before. Enjoy wildlife at a distance that does not cause the animals to react, and report any unusual situations to experienced wildlife managers or rehabilitators.


Anthony, S.J., St. Leger, J.A., Pugliares, K., et al. Emergence of fatal avian influenza in New England harbor seals. (2012) mBio. Accessed November 17, 2012.

Payungporn S, Crawford PC, Kouo TS, Chen L, Pompey J, Castleman WL, et al. 2008 Influenza A virus (H3N8) in dogs with respiratory disease, Florida. Emerging Infectious Diseases. Accessed November 17, 2012.

Jensen T, van de Bildt M, Dietz HH, Andersen TH, Hammer AS, Kuiken T & Osterhaus, A (2002). Another phocine distemper outbreak in Europe. Science 297: 209-209. Accessed November 17, 2012.

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