The outbreak was first discovered along Alaska’s North Slope, where severely ill and dead ringed seals were found with excessive hair loss and lesions on their faces and flippers.
Similar mysterious deaths have been reported in Canada and Russia, and the illness may have spread to other species including, spotted seals, bearded seals and walruses.
The environmental agency NOAA says tests have ruled out viruses, including some that killed hundreds of seals in Europe during 1988.
“A group of international wildlife researchers continue to test for a wide range of possible factors, including bacterial, viral, fungal, or toxic agents that may be responsible for the animals' condition,” NOAA said in a statement.
Alaska State Veterinarian Bob Gerlach said that this may not be a problem just for marine mammals.
He fears it “could be a reflection of a larger problem across the entire Arctic coastal ecosystem.”
Native residents along Alaska’s Arctic coast have been warned not to eat sick animals or feed the meat to their dogs in case the pathogen can infect other species.