On May 23, 2025, the U.S. Centers for Disease Control and Prevention, University of Alaska Anchorage, ans Colorado State University reported they have identified fatal tularemia in two stranded beluga whales in Cook Inlet, Alaska. The early release article is published in Emerging Infectious Diseases.

Francisella tularensis was detected by nanopore metagenomics, confirmed by quantitative PCR and immunohistochemistry, and characterized as F. tularensis subspecies holarctica by multilocus sequence typing.

Francisella tularensis is a highly pathogenic gram-negative bacterium that infects a large range of animals and humans, primarily in the Northern Hemisphere, causing the clinical disease tularemia. Human disease manifests with influenza-like symptoms (lymphadenopathy, conjunctivitis, pneumonia, septicemia) and other specific symptoms corresponding to the route of exposure. Two subspecies, F. tularensis subsp. tularensis and holarctica, are known pathogens and can be acquired via multiple routes, including arthropod vector, cutaneous, ingestion, or inhalation.

F. tularensis was first documented in Alaska, USA, in 1938 and has been isolated infrequently in ticks, lagomorphs, and rodents. Serologic studies have confirmed exposure in humans, avian species, terrestrial mammals, and polar bears in multiple areas of the state.

In October 2023, tularemia was diagnosed in a seal in Washington, USA, when a biologist was infected during necropsy. The same fall, dead stranded beluga whales (Delphinapterus leucas) in Cook Inlet, Alaska, were found to have gross lesions consistent with tularemia.

One human case of tularemia was reported in Cook Inlet’s largest adjacent city in 2023, however, the circumstances of exposure were not reported. The propensity of whales to travel long distances could further disseminate this pathogen, increasing exposure to humans and wildlife.

The findings highlight a new risk to persons working in the marine environment and should be considered when assessing biosecurity and marine mammal health in the North Pacific.