Concern for Highly Pathogenic Avian Influenza Spillover into Cetaceans.

Area of Science:

• Veterinary Virology
• Marine Mammal Health
• Wildlife Disease Ecology

Background:

• Influenza A virus (IAV) infects diverse hosts, posing pandemic risks.
• The H5N1 subtype of avian influenza is currently causing a panzootic, impacting wildlife globally.
• Environmental changes facilitate the spread of HPAI H5N1, leading to spillover events into marine ecosystems.

Purpose of the Study:

• To investigate the occurrence and characteristics of Influenza A virus (IAV) infections in cetaceans.
• To analyze viral genetic markers associated with mammalian adaptation in H5N1 isolates from cetaceans.
• To evaluate the transmission dynamics of H5N1 between seabirds, marine mammals, and cetaceans.

Main Methods:

• Analysis of molecular markers in 21 H5N1 cetacean isolates.
• Phylogenetic analysis of hemagglutinin (HA) and polymerase basic protein 2 (PB2) sequences.
• Comparison of viral sequences from cetaceans, seabirds, and other marine mammals.

Main Results:

• Mutations associated with mammalian adaptation were identified in HA, PB2, and NP viral proteins of H5N1 cetacean isolates.
• Phylogenetic analyses did not support sustained H5N1 transmission among cetaceans.
• Evidence suggests H5N1 spills over into cetaceans from seabirds and potentially other marine mammals.

Conclusions:

• Cetaceans are susceptible to HPAI H5N1, with evidence of viral adaptation to marine mammals.
• Current data do not indicate efficient or sustained H5N1 transmission within cetacean populations.
• Enhanced global surveillance of IAV in cetaceans is critical for pandemic preparedness and marine ecosystem health.