Updated June 24, 2024
In January 2022, the state of South Carolina reported a case of highly pathogenic avian influenza in a wild bird—the first detected case of this virus subtype in the United States since 2016, likely introduced from Canada late in 2021. Since then, the virus has spread across the U.S., affecting both coasts with multiple separate introductions. As of 2024, this outbreak continues to cause significant issues, and has even reached dairy cows in Texas, Kansas, Michigan, New Mexico, South Dakota, Idaho, North Carolina, and Ohio.
Understanding the Threat
This virus belongs to the influenza A H5N1 subtype and is classified as “highly pathogenic” (HPAI), which specifically refers to its ability to kill chickens and other domesticated poultry species. While highly pathogenic H5N1 strains pose limited threats to wild birds (and to human health), infected poultry have high death rates—nearly 100%. Most commercial flocks infected with highly pathogenic H5N1 are “depopulated” (i.e., culled) and removed from commercial food supply chains, posing major economic losses for the agricultural industry and potential food price hikes and shortages for consumers.
Highly Pathogenic Avian Influenza Strains
Like other influenza viruses, A(H5N1) is characterized by the type of hemagglutinin (H) and neuraminidase (N) proteins present on the virus’s surface. Hemagglutinin proteins bind to receptors on the cell surface and facilitate viral infection, and neuraminidase enzymes aid viral release from infected cells.
While most influenza A viruses are considered “low pathogenicity”, all known highly pathogenic influenza A viruses display the H5 or H7 hemagglutinin subtypes. The enhanced ability of highly pathogenic H5- and H7-bearing viruses to infect hosts is thought to be due in part to a cleavage site on the hemagglutinin protein that allows viral replication to take place beyond the respiratory and gastrointestinal tracts (1–3).
When birds are infected with A(H5N1), they can shed the virus in their saliva, nasal discharge and feces. Surfaces and bodies of water contaminated with the virus can also infect other birds. Wild waterfowl species appear to be natural reservoirs of the virus, which hinders eradication (4).
Typical biosecurity measures for commercial and backyard poultry flocks mainly focus on preventing flocks’ contact with materials—ponds, feed, clothing—that might be contaminated with the virus. If disease is detected in a flock, the flock is depopulated. Routine testing of wild waterfowl through cooperation with hunters is also an important part of the USDA’s Animal and Plant Health Inspection Service’s avian influenza biosecurity program.
The strain driving the current US outbreak belongs to the Eurasian lineage goose/Guangdong/1/1996 lineage H5 clade 2.3.4.4b, which has become the most common H5N1 strain detected globally. A pre-print released by the USDA National Wildlife Research Center in February suggests that, based on genetic analysis of virus samples collected in South Carolina, US cases spread from Europe through birds with trans-Atlantic migrations (5). If so, this is the first documented trans-Atlantic transmission of this virus strain (6).
Avian Influenza and Humans
The CDC lists the current A(H5N1) outbreak as a low risk to humans. Current and past variants of A(H5N1) have demonstrated low transmission from birds to humans. Most human cases have been in people who work in the poultry industry and have a high level of exposure to infected birds.
However, because of the tendency for influenza viruses to mutate, highly pathogenic A(H5N1) represents a potential future human health risk. Recognizing the potential public health impact of avian influenza, the CDC is developing various vaccines for several avian influenza subtypes. The current A(H5N1) virus in circulation has been found to be “nearly identical” to one of these vaccine candidates. In the chance that sustained human-to-human transmission was detected, vaccines like this one could be manufactured and deployed.
In the meantime, surveillance efforts in bird flocks continue. For people in the poultry industry or who have backyard flocks, standard biosecurity practices are the most tractable steps to take to protect their birds and their own health.
US Economic Impact
The H5N1 outbreak has made a severe economic impact, notably causing egg prices to skyrocket due to a sharp decline in supply while demaind has remained steady. For example in 2022, the average price for a dozen eggs rose dramatically from less than $2.00 to $5.37, reflecting a 278% increase from the start to the end of the year (7). Here again in 2024, we are seeing similar trends with egg prices.
H5N1 avian influenza has notably spread to dairy cows, a significant and concerning development (8). The initial cases in cattle emerged in Texas by late March 2024, with symptoms that led to a confirmed diagnosis of avian influenza (9). This transmission poses potential threats to the dairy industry, as affected cows have reduced milk production and appetite, potentially leading to economic set backs from decreased milk sales and the costs of treating ill animals.
According to the FDA and USDA, the commercial milk supply remains safe because all products undergo pasteurization before market release (10). Dairies are mandated to process milk only from healthy animals; any milk from affected cows is either diverted or destroyed to prevent it from entering the human food chain. Pasteurization processes have been consistently effective in eliminating pathogens, including viruses like influenza, from milk.
How Promega Is Helping
Promega provides a range of molecular biology solutions to help scientists and technicians address the challenges posed by Highly Pathogenic Avian Influenza and other similar pathogens, including products and instruments that can be used for monitoring, vaccine research and development as well as in research to understand the efficacy and potency in therapeutics research and development.
We provide high-quality nucleic acid purification chemistries essential for reliable blood, tissue and oral sample extraction. Extraction from these sample types is amenable to our automated systems like the Maxwell® RSC 48, supporting high-throughput needs, ensuring efficiency and scalability. Our sample preparation technology is complemented by sample analysis tools such as the GoTaq® Enviro qPCR and RT-qPCR Systems, which have been specifically designed for real-time PCR applications, useful precise and rapid identification viral nucleic acid amplification from more complex and challenging matrices.
Products like our RiboMax™ Large Scale RNA Production Systems are applicable for vaccine research and development and any application requiring large-scale mRNA production. In vaccine research and development, cell-based assays including the CellTiter-Glo® Lumienscent Cell Viability Assay among others can assess vaccine potency and toxicity. Our PureYield™ Plasmid Midiprep System, ensures production of high-quality, endotoxin-free plasmid DNA suitable for sensitive downstream applications including eukaryotic transfection, in vitro transcription and coupled in vitro transcription/translation.
These comprehensive solutions enable Promega to support scientists and technicians around the globe to detect, monitor and manage HPAI and other pathogen outbreaks, advancing safety and health standards in the animal health industry.
References
- Senne, D. A., et al. (1996) Survey of the Hemagglutinin (HA) Cleavage Site: Sequence of H5 and H7 Avian Influenza Viruses: Amino Acid Sequence at the HA Cleavage Site as a Marker of Pathogenicity Potential. Avian Dis. 40, 425–437.
- Rott, R., et al. (1995) Influenza Viruses, Cell Enzymes, and Pathogenicity. Am. J. Respir. Crit. Care Med. 152, S16–S19.
- Boggs, J., et al. (2010) Highly Pathogenic H5N1 Influenza Viruses Carry Virulence Determinants Beyond the Polybasic Hemagglutinin Cleavage Site. PLoS One 5, e11826.
- Sonnberg, S.; Webby, R. J.; Webster, R. G. (2013) Natural History of Highly Pathogenic Avian Influenza H5N1. Virus Res. 178, 63–77.
- Bevins, S. N., et al. (2022) Intercontinental Movement of H5 2.3.4.4 Highly Pathogenic Avian Influenza A(H5N1) to the United States, 2021. [bioRxiv preprint] https://doi.org/10.1101/2022.02.11.479922
- Caliendo, V., et al. (2022) Transatlantic Spread of Highly Pathogenic Avian Influenza H5N1 by Wild Birds From Europe to North American in 2021. [bioRxiv preprint] https://doi.org/10.1101/2022.01.13.476155
- USDA Economic Research Service. US Department of Agriculture. Wholesale egg prices tumble as egg supplies recover. [Internet: https://www.ers.usda.gov/data-products/chart-gallery/gallery/chart-detail/?chartId=106845 Accessed June 24, 2024]
- USDA Animal and Plant Health Inspection Service. Detections of Highly Pathogenic Avian Influenza (HPAI) in Livestock. [Internet: https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock Accessed June 24, 2024]
- USDA. USDA , HHS Announce New Actions to Reduce Impact and Spread of H5N1. [Internet: https://www.usda.gov/media/press-releases/2024/05/10/usda-hhs-announce-new-actions-reduce-impact-and-spread-h5n1 Accessed June 24, 2024]
- FDA. Milk Safety and Supply. [Internet: https://www.fda.gov/food/milk-guidance-documents-regulatory-information/questions-and-answers-regarding-milk-safety-during-highly-pathogenic-avian-influenza-hpai-outbreaks#safetyandsupply Accessed June 24, 2024}
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