Frequent Questions—Maine Seal Stranding Event

Why are you closing the Unusual Mortality Event?

The conditions under which the UME was declared are no longer occurring or have become persistent. The UME Investigative Team determined the cause of the UME was spillover events of the highly pathogenic avian influenza H5N1 virus from infected wild birds to harbor and gray seals. Positive cases and elevations in gray and harbor seal strandings occurred for a discrete time (June 20 to July 20, 2022) along the coast of Maine. All stranded seals sampled outside of the UME area (Maine) tested negative.

How widespread was this Unusual Mortality Event?

Increased numbers of dead harbor and gray seals were detected along the coast of Maine including York, Cumberland, Sagadahoc, Lincoln, Knox, Waldo, Hancock, and Washington Counties.

What were the dates for this UME? How many seals were included?

The UME occurred between June 20 to July 20, 2022 with 181 seals (143 harbor seals, 28 gray seals, and 10 seals of unidentified species) stranding in Maine.

What do scientists believe is the most likely cause of this UME?

It was due to spillover events of the highly pathogenic avian influenza H5N1 virus from infected wild birds (gulls, eiders, terns) to harbor and gray seals. This conclusion is supported by the findings of:

• HPAI virus in 58 percent of seals (19 out of 33) tested during a discrete period of time located near dead and dying wild birds infected with HPAI 
• Increased strandings of harbor and gray seals during this period of time of positive HPAI seal cases 
• Respiratory lesions consistent with avian influenza in 10 of the seals that tested positive, and neurologic lesions in five of these seals on histopathologic evaluation
• Sequencing of the H5N1 virus (HPAI 2.3.4.4b) detected in seals showed that the seals were infected with the same virus as wild birds. 

Additionally, significant post-UME monitoring of seals for HPAI from July 2022 through June 2023 has not detected an additional spillover event in seals or any positive seal cases, even though HPAI is still circulating in wild bird populations. The seal populations have also gone through both the molting and pupping seasons (which can be physiologically stressful) without additional spillover events in the area. Lastly, there was no evidence of phocine distemper virus in tested seals. 

Were other mammals or animals affected by this die-off event?

There is an ongoing global outbreak event involving highly pathogenic avian influenza H5N1. It began in 2021 and has been detected in domestic and wild birds and some species of terrestrial mammals across the United States (e.g., red fox, striped skunk, opossum, raccoon, bobcat, American mink, coyote, fisher cat, bear, river otter). More information can be found at U.S. Department of Agriculture, National Wildlife Health Center, and Centers for Disease Control and Prevention.

Was this influenza outbreak in seals associated with the larger avian flu outbreak in North America?

The current outbreak of highly pathogenic avian influenza in North America was first detected in early winter 2021 in Newfoundland and Labrador, Canada. It has now been confirmed in nearly all U.S. states and all Canadian provinces. It has been found in commercial poultry, backyard flocks, many species of wild birds, and several species of mammals.

What is next now that the Unusual Mortality Event has been closed?

Scientists plan to continue post-UME monitoring of harbor and gray seals in Maine. Sampling will focus on swab collection (oral, nasal, ocular, and rectal) from live to moderately decomposed seals, and necropsy from limited cases of euthanized or fresh dead seals. Swabs will also be collected opportunistically from seal strandings in New Hampshire through North Carolina. Scientists will also collect samples from wild seals during capture-and-release health assessments or tagging work. Post-UME swab testing is being supported by Tufts University.

What are influenza viruses?

There are three types of influenza viruses: A, B and C. Avian influenza A viruses, which include the virus that was detected in seals in 2022, occasionally cross over the species barrier from birds. They cause clinical disease and epidemics in people and other mammals, including seals. These are known as “zoonotic diseases,” meaning they have the potential to spread between animals and people (and their pets). Influenza B viruses are primarily a virus in people with no known wildlife reservoir, and cause clinical disease epidemics in people. . 

Influenza C is a virus that infects people and may cause a mild respiratory illness but is not thought to cause epidemics in people.

Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: hemagglutinin (H) and the neuraminidase (N). There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes. Influenza A viruses can be further broken down into different strains. Subtypes may be species specific, so not all subtypes are found in all species. 

Learn more about flu viruses.

What is avian influenza?

Avian influenza, or bird flu, refers to a respiratory disease caused by infection with a type of influenza virus. Avian flu viruses normally spread among wild water birds, such as ducks and geese. These viruses can spread to domestic poultry, such as chickens, ducks, geese, and guinea hens. Avian flu viruses do not normally make humans sick, but human infections with avian flu viruses have occurred. People who have regular contact with poultry or wild birds are most at risk.

What is the risk to humans from influenza viruses?

Some influenza viruses are “zoonotic diseases,” which means they can be shared between animals and people. Influenza A viruses have a relatively high rate of mutation, or change, which may allow them to cross species barriers and may cause severe disease in their new hosts. The Centers for Disease Control, the National Wildlife Health Center, National Institute of Health, state agencies, and other organizations like NOAA monitor events involving animal influenza viruses very closely. We advise the public to take precautions for themselves and their pets.

What is the risk to humans from the highly pathogenic avian influenza H5N1virus?

According to the CDC, the health risk posed to the general public is low; however, they recommend precautions. People and their pets should avoid all contact with sick or dead wildlife because HPAI can spread between animals and people (and their pets). Although the risk of infection to the general public remains low, beachgoers should not touch live or dead seals or allow pets to approach seals. They should maintain a safe distance of 150 feet.

Does eating seafood pose a risk?

No. Influenza viruses do not cause disease in fish, so there is no risk of catching this virus by eating fish.

Are there any risks to pets?

Yes. Dogs and cats also share infectious diseases with marine mammals. They should not be allowed to approach live or dead marine mammals and wildlife, or to consume dead marine mammals and wildlife or their parts. Dogs are susceptible to a canine influenza virus. Additionally, sick seals may bite you or your pet if you get too close. NOAA Fisheries recommends contacting your pet’s veterinarian to discuss the potential risk to pets in your local area, or if your pet bites or is bitten by a seal.

How does influenza virus spread among seals?

Influenza viruses are usually spread through inhalation of respiratory particles, direct contact with feces, or between animals, including between mothers and pups. Animals can also be exposed to the virus through other entryways such as the eyes, mouth, stomach, skin wounds, and the urogenital tract.

How do seals catch influenza?

While this is still an area of active investigation, we believe most cases initiate from waterfowl or seabirds, which are the natural reservoirs for a diverse range of Influenza A variants. Seals can be exposed by being close to birds through respiratory droplets or exposure to infected bird feces. Once a new variant of influenza has entered into a seal population, it is then often able to spread from seal to seal.

How do influenza viruses affect seals?

The most common organs affected are the lungs and brain. Sick animals may appear thin, have respiratory clinical signs such as coughing or difficulty breathing, and may exhibit teary eyes, lethargy, and/or abnormal behavior due to a brain infection.

Where can I find additional information on harbor and gray seals and other Unusual Mortality Events?

Visit our website to find more information on Harbor Seals, Gray Seals, and other Unusual Mortality Events.

What should people do if they encounter a dead or live-stranded harbor or gray seal on the beach?

The most important step members of the public can take to assist investigators is to immediately report any sightings of seals in distress or dead stranded seals. In Maine, please call the Maine Marine Animal Reporting Hotline at (800) 532-9551. To report seal strandings south of Maine, please call the NOAA Fisheries Stranding Hotline at (866) 755-6622. Do not approach or touch the seal, and keep your pets far away.

What should people do if they witness harassment or any marine mammal violation in the water or on the beach?

To report violations, please contact NOAA’s Office of Law Enforcement at (800) 853-1964.

What is the UME Contingency Fund?

The Marine Mammal Unusual Mortality Event Fund is used by the Secretary of Commerce, in consultation with the Secretary of the Interior:

• To compensate persons for special costs incurred in acting in accordance with the contingency plan issued under section 1421c(b) of this title or under the direction of an Onsite Coordinator for an unusual mortality event

• For reimbursing any stranding network participant for costs incurred in preparing and transporting tissues collected with respect to an unusual mortality event for the Tissue Bank

• For care and maintenance of marine mammals seized under section 1374(c)(2)(D) of this title”

The National Contingency Plan for Response to Unusual Marine Mammal Mortality Events outlines the types of expenses that are reimbursable under the fund and the process for requesting reimbursement. 

Learn more about the UME Contingency Fund.

How can deposits be made into the UME Contingency Fund?

The following can be deposited into the fund:

• Amounts appropriated to the fund
• Other amounts appropriated to the Secretary for use with respect to UMEs
• Amounts received by the United States in the form of gifts, devises, and bequests under subsection (d) of section 405(d) of the Marine Mammal Protection Act

The public may use Pay.gov to donate to the UME Contingency Fund for this or other UMEs and help cover costs incurred by the Marine Mammal Stranding Network.