European Bison - Credit Wikipedia
#19,092
It was 2 years ago this week (March 24th, 2024) that I wrote about Curious Reports of Unknown Disease In Dairy Cows (Texas, Kansas & New Mexico), that in short order would be identified as HPAI H5N1.
Since then we've seen more than 1,000 dairy herds infected with HPAI H5 in the United States, along with spillovers to goats, pigs, and alpacas. Testing remains largely voluntary, however, and some estimates suggest that significant under-reporting of H5N1 in dairy herds is likely.HPAI testing appears to have been delayed for several weeks because - up until then - cattle had been considered poorly susceptible to influenza A (see A Brief History Of Influenza A In Cattle/Ruminants), despite successful experimental infection with H5N1.
Over the past two years we've seen a number of studies suggesting that Influenza A in general (including HPAI H5), can and does infect livestock, including bovines, pigs, and goats. A few of many studies include:
Netherlands: NOS.NL Reports 5 Dairy Cows Have Now Tested Positive for H5N1
Preprint: Highly Pathogenic Avian Influenza H5 Virus Exposure in Goats and Sheep (in Pakistan).
Germany FLI: Statement On Experimental Infection Of Dairy Cows With European H5N1 Virus
Despite this growing resume, much of the world continues to act as if the spillover of HPAI H5 is somehow just an `American problem' - due to an aberrant local strain of the virus - and unlikely to spread beyond our borders.
But it isn't at all clear how seriously governments and farmers are taking these recommendations - both here in the United States - and around the world.
Today we've another (admittedly minor) data point; The first detection of influenza A (H1N1pdm) in a European Bison. This comes from a retrospective study, using samples collected between 2017 and 2023, and the positive sample came from 2018.
This report is notable because it adds yet another wild ruminant species to the list of influenza A susceptible mammals, and it highlights the risks of bidirectional spillover of IAV at the wildlife-livestock-human interface.Almost all of the testing of cattle for HPAI in the United States (and elsewhere) has been conducted on lactating cows, but this detection was in a 4 year-old male bison which lived at a farm in Poland.
Brief Report
Open access
Published: 21 March 2026
Volume 50, article number 212, (2026)
Veterinary Research CommunicationsAnna Didkowska, Víctor Martín-Santander, Anna Golke, Marlena Wojciechowska, Wanda Olech, Olga Szaluś-Jordanow, Tomasz Dzieciątkowski, Álex Gómez, Sergio Villanueva-Saz, Ewelina Kwiecień, Pablo Quilez, Krzysztof Anusz & Diana Marteles-Aragüés
Abstract
Influenza A virus is a zoonotic pathogen capable of infecting a wide range of hosts, yet data on infections in wild ruminants are limited. The European bison (Bison bonasus), Europe’s largest terrestrial mammal, had not previously been identified as a host for Influenza A virus. This study aimed to provide the first molecular and serological evidence of H1N1 pandemic influenza A virus (A/H1N1pdm) infection in European bison, contributing to the understanding of Influenza A virus ecology at the wildlife–livestock interface.
We retrospectively analysed 335 serum samples collected from European bison between 2017 and 2023 using a commercial ELISA detecting antibodies against all Influenza A virus subtypes. Tissue samples (heart and liver) from ELISA-positive animal were further tested by RT-qPCR targeting hemagglutinin (HA) and neuraminidase (NA) genes of A/H1N1pdm, A/H3N2, and A/H5N1. PCR-positive products were sequenced for confirmation.
Seroprevalence of Influenza A virus was 0.3% (1/335; 95% CI: 0.02–1.71). Influenza A virus RNA (A/H1N1pdm) was detected in the heart and liver tissue of a 4-year-old captive male from Borecka Forest, culled in 2018. The animal exhibited pulmonary congestion, emphysema, and posthitis at necropsy.
This study provides the first molecular and serological confirmation of H1N1pdm infection in European bison. The findings highlight the potential susceptibility of this species to Influenza A virus and raise questions about possible transmission routes, including spillover from domestic animals or humans.
We saw similar detections of (of non-HPAI) influenza A reported in steers and bulls last year in Virology: Detection of Antibodies Against Influenza A Viruses in Cattle, where the authors wrote:
Our results demonstrate that IAVs other than H5N1 can infect cattle, infections are not limited to dairy cows, and that bovine infections with swine and human IAVs have occurred prior to the H5N1 outbreaks.
All results highlight the value in monitoring IAV epidemiology in cattle, as the viruses might adapt to cattle and/or reassort with the currently circulating H5N1 HPAIV, increasing risk to humans.
Yesterday, in Referral: (OFFLU Report) Beyond poultry: Rethinking monitoring and control of HPAI H5Nx anticipating spillover risks for mammals, we saw renewed calls for enhanced surveillance of farmed animals: particularly cattle, goats, sheep, fur bearing mammals, and pigs.
Last December more than 30 countries participated in a WPRO Table-Top Exercise Crystal: A `Bovine' Novel Flu Outbreak Scenario;' one which envisioned an epidemic that would have been considered by many as bordering on the absurd just 24 months ago.
Today, due to the speed at which HPAI is evolving, it is all too plausible.
