H5N1 in Pigs: An Emerging Threat and the Urgent Need for a “One Health” Response

According to a recent study, the highly pathogenic avian influenza H5N1 clade 2.3.4.4b is evolving at an accelerated rate, with genotypes B3.13 and D1.1 recently detected in dairy cattle, poultry, wild birds, wild mammals, and humans; and, in a new development, the D1.2 genotype has been detected in free-range pigs. According to the authors, the pork industry and public health now face a shared risk that requires coordinated responses through a “One Health” approach.  

What Has Changed

Pigs play a pivotal role in the ecology of influenza viruses. In this context, the emergence of the H5N1 2.3.4.4b virus at the interface between livestock, wildlife, and humans changes the equation: the presence of the virus in multiple domestic and wild hosts increases opportunities for interspecies transmission, with potential consequences for herd health security, food safety, and, ultimately, pandemic risk. The authors describe an evolving situation, with multihost circulation of recent genotypes, detection in dairy cattle herds, and human cases in several regions of the world, indicating a faster epidemiological dynamic than previously observed. In this context, the detection of D1.2 in free-range pigs serves as an early warning sign that the swine reservoir could, in turn, enter the transmission chain.  

Gaps to Be Filled

The study lists the areas of uncertainty that hinder prevention: What is the actual susceptibility of pigs to the different 2.3.4.4b genotypes? What are the dominant shedding kinetics and modes of transmission (pig-to-pig, species-to-species)? Which farming factors (free-range, contact with wildlife, mixing of species) increase the risk of infection? And what would be the operational consequences for the industry of an outbreak of highly pathogenic avian influenza in pigs? These gaps in our understanding of viral circulation warrant further research and priority surveillance.  

What the “One Health” Approach Could Contribute

The authors call for preventing the introduction of H5N1 into swine farms and minimizing transmission pressure through evidence-based strategies: targeted surveillance at the wildlife-livestock interface, harmonized sampling and diagnostic protocols, rapid data sharing between animal health and human health sectors, biosecurity measures tailored to on-the-ground realities, and training of teams on zoonotic risk. Objective: to ensure food safety, the resilience of production systems, and to reduce the likelihood of human infections, including in scenarios of widespread transmission.  

Implications for pig farms

In practical terms, the challenge is to block the virus’s entry points by reducing contact with wildlife (managing water sources, reducing the attractiveness of farm buildings), by separating species on mixed-species farms, by strengthening hygiene and clinical surveillance of exposed animals and farmers, and by streamlining the flow of information between veterinarians, government agencies, and authorities responsible for human health. In areas with high circulation of the H5N1 virus, active surveillance and pre-established response plans are necessary to prevent silent spread. The risk is very real: the current dynamics of H5N1 clade 2.3.4.4b create conditions conducive to the involvement of pigs in the transmission cycle. As long as gaps remain, the safest option remains the “One Health” approach to anticipate the virus’s incursion, accelerate its detection, and sever the links between animal reservoirs and humans.