Atlantic Seals Dying of Avian Flu

Beginning in June 2022, Marine Mammals of Maine (MMoME)—a NOAA Fisheries authorized marine mammal stranding network partner—has responded to an elevated number of stranded seals. Most of the seals were found dead. On July 1, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service’s National Veterinary Services Laboratories confirmed that samples from four-stranded seals in Maine have tested positive for Highly Pathogenic Avian Influenza H5N1. All of these animals had recently died or required euthanasia. USDA is notifying the Centers for Disease Control and Prevention as well as state animal and public health officials. The finding will be reported to the World Organization for Animal Health.

The current rate of dead seal strandings in this area is approximately three times the normal rate for this time of the year. During elevated stranding events such as this, the Marine Mammal Stranding Network collaborates with NOAA Fisheries to further investigate. They consider environmental conditions, common factors contributing to past stranding events, and any potential human impacts. They also obtain information on the causes of illness and death in the seals. The Network will continue to collect and analyze as new cases are documented. Response, recovery and sampling protocols for seals are in place and being led by MMoME. 

Seal mortality events have occurred in southern Maine previously. The most recent Unusual Mortality Event in seals occurred in 2018 due to phocine distemper virus. These events can last for several months to several years. They are challenging when the event involves infectious diseases with the potential for spread across wildlife species and domestic animals or humans.