First Detection of the H1N1 Virus Reported in European Bison

A study reports the first serological and molecular detection of the influenza A(H1N1) virus in European bison. The study retrospectively analyzed 335 serum samples collected from bison between 2017 and 2023 and identified only one positive animal, representing an overall seroprevalence of 0.3%. The influenza A virus is capable of infecting a wide range of hosts, but data on infections in wild ruminants remain limited. The European bison (Bison bonasus ), Europe’s largest land mammal, had never before been identified as a host for the influenza A virus. Influenza A(H1N1) virus RNA was detected in the heart and liver tissues of a 4-year-old captive male bison from the Borecka Forest in Poland, which was culled and sampled in 2018. At necropsy, the animal exhibited pulmonary congestion, emphysema, and post-inflammation. These findings highlight this species’ potential susceptibility to the influenza A virus and raise questions about possible sources and routes of transmission, particularly from domestic animals or humans. The confirmation of a naturally occurring A/H1N1 infection in a large ruminant, prior to the H5N1 influenza epizootic among dairy cattle in the United States in 2024, constitutes preliminary evidence regarding the risk of interspecies transmission among bovids, according to the “One Health” approach. This significance is reinforced by growing retrospective evidence that cattle may be exposed to multiple subtypes of influenza A viruses, including those of human and swine origin, as documented by recent serological studies. This study adds the European bison to the list of species susceptible to influenza A and underscores the need for increased surveillance in environments where wildlife and domestic animals interact closely.