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Rapid Diagnosis of Avian Influenza Virus in Wild Birds: Use of a Portable rRT-PCR and Freeze-dried Reagents in the Field
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Mass mortality events in aquatic mammals caused by avian influenza viruses

Monica Mirolo1, Martin Ludlow1, Albert Osterhaus1

  • 1Research Center for Emerging Infections and Zoonoses (RIZ), University of Veterinary Medicine, Hannover D-30559, Germany.

Current Opinion in Virology
|July 13, 2026
PubMed

Insights

Highly pathogenic avian influenza virus (AIV) infections, particularly subtype A(H5N1), are causing severe disease and mortality in aquatic mammals. Further surveillance is crucial to assess risks to wildlife and public health.

Area of Science:

  • Veterinary Virology
  • Wildlife Disease Ecology
  • Infectious Disease Epidemiology

Background:

  • Mass mortality events (MMEs) in aquatic mammals are often linked to morbillivirus or avian influenza virus (AIV) infections.
  • While AIVs in mammals were historically linked to bird contact, evidence of mammalian adaptation, including specific RNA mutations, is emerging.
  • Highly pathogenic AIV (HPAIV) subtype A(H5N1) clade 2.3.4.4b is causing severe neurological disease and mortality in marine mammals.

Purpose of the Study:

  • To investigate the role of AIV in aquatic mammal MMEs.
  • To understand the adaptation and transmission dynamics of AIV in marine mammal populations.
  • To assess the implications of AIV in aquatic mammals for conservation and public health.

Main Methods:

  • Analysis of genetic and phenotypic characteristics of AIVs from affected aquatic mammals.
  • Serological surveys to detect AIV antibodies in pinniped and cetacean populations.
  • Review of epizootic data and case histories of AIV infections in marine wildlife.

Main Results:

  • HPAIV A(H5N1) clade 2.3.4.4b is associated with significant mortality and neurological signs in pinnipeds and cetaceans.
  • Limited evidence for enzootic AIV circulation in aquatic mammals; antibodies are transient or undetectable post-HPAIV infection.
  • Documented 'mammalian-adapting mutations' in HA or PB2 segments of AIVs in aquatic mammals.

Conclusions:

  • AIV, especially HPAIV A(H5N1), poses a significant threat to aquatic mammal populations, causing severe disease and mortality.
  • Understanding AIV adaptation and transmission in marine mammals is critical for managing endangered species.
  • Ongoing surveillance and genetic characterization of AIVs in aquatic mammals are essential for both wildlife and public health protection.

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