QUARTERLY BEAT
APRIL 2026
Bird flu isn’t just a poultry problem anymore. In this VETgirl Webinar, Not Only for the Birds: Implications of Highly Pathogenic Avian Influenza for Poultry and Other Animals on January 8, 2026, Dr. Jessica Higgins, GCAHM breaks down what highly pathogenic avian influenza (HPAI) actually is, why this current H5N1 outbreak is different from influenza subtypes, and what veterinarians need to know about transmission between species. In case you missed the webinar, watch it again HERE or read the cliff notes below! NOT ONLY FOR THE BIRDS: IMPLICATIONS OF HIGHLY PATHOGENIC AVIAN INFLUENZA FOR POULTRY AND OTHER ANIMALS Dr. Jessica Higgins, GCAHM WEBINAR HIGHLIGHTS
Avian influenza has attracted significant attention in recent years. Terms like “bird flu” and “H5N1” appear frequently in the news, sometimes alongside the word “pandemic,” often used inaccurately, as reports extend to infections in species well beyond poultry. The expanding host range of the virus has raised important questions for veterinary professionals: What exactly is avian influenza? How does it spread across species? And what are the implications for animal and public health? This article provides a practical overview of avian influenza, focusing on the current Highly Pathogenic Avian Influenza (HPAI) H5N1 outbreak, its growing host range, and considerations for veterinarians working with multiple species.
Since avian influenza is caused by Influenza A viruses, the remainder of this discussion focuses on this genus. Influenza A viruses are classified based on two surface proteins: hemagglutinin (HA) and neuraminidase (NA). There are 18 HA and 11 NA subtypes, forming combinations such as H5N1. Although 144 HA–NA combinations are theoretically possible, not all occur naturally or infect every host species. Wild aquatic birds host the greatest diversity of Influenza A viruses and act as the primary natural reservoir. These birds often carry viruses without showing clinical signs, shedding them into the environment through feces and respiratory secretions. This silent circulation facilitates infection of domestic poultry and other mammals. Additionally, migratory flyways facilitate intercontinental spread and viral reassortment, creating more opportunities for the virus to evolve and infect new hosts.
UNDERSTANDING INFLUENZA
Influenza viruses belong to the Orthomyxoviridae family and are single-stranded RNA viruses with segmented genomes. This genetic structure allows for frequent mutation and reassortment, enabling influenza viruses to adapt quickly and infect new hosts. Four genera are recognized: Influenza A, B, C, and D. GENERA OF INFLUENZA VIRUSES AND HOST RANGE: • Influenza A: Infects birds, humans, and numerous mammalian species. It is responsible for seasonal influenza epidemics and all known global influenza pandemics. Avian influenza viruses fall within this group. • Influenza B: Primarily infects humans, with occasional spillover into other species. It is associated with seasonal flu outbreaks but not pandemics. • Influenza C: Causes generally mild disease in humans and swine. • Influenza D: First identified in 2011, with dairy cattle now recognized as the primary reservoir. While seropositivity has been detected in cattle workers, productive human infection has not been documented.
AVIAN INFLUENZA IN DOMESTIC POULTRY
Domestic poultry such as chickens, turkeys and quail are highly susceptible to avian influenza viruses. The disease is classified as low pathogenic (LPAI) or highly pathogenic (HPAI) based on its impact in poultry. LPAI usually causes mild or subclinical disease, such as reduced egg production or minor respiratory signs. H5 and H7 subtypes of LPAI are closely monitored due to their potential to mutate into highly pathogenic forms. HPAI causes high morbidity and mortality, often resulting in sudden death across flocks. Additional clinical signs of HPAI in poultry can include a marked drop in egg production, swelling of the eyelids, comb, wattles, and shanks, and purple discoloration of the comb and legs. Respiratory signs such as coughing and nasal discharge may be present, as well as neurologic signs including torticollis, ataxia, or paralysis, and diarrhea. Historically, HPAI has been limited to H5 and H7 subtypes, although any Influenza A virus meeting federal criteria may be classified as highly pathogenic. It is important to note that “highly pathogenic” refers specifically to disease severity in domestic poultry and
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