Experiments conducted at the Scripps Research Institute funded by the National Institute of Health demonstrated the role of the Q226L mutation coding for viral hemagglutinin. The gene allows H5N1 virus to attach to receptors on cells lining the human respiratory tract. The study was conducted on H5N1 A/Texas/37/2024 isolated from the first patient infected with the virus circulating in a dairy herd. Presence of the Q226L mutation does not necessarily represent the potential for human-to-human transmission (contagion) as this capability would require additional mutations.
The Scripps finding is consistent with warnings expressed by virologists and epidemiologists that control of H5N1 infection in poultry and dairy herds should be intensified using all appropriate and available modalities. The APHIS reliance on “stamping out” infections as they are diagnosed is clearly not working. This is evidenced by the extended duration of the current epornitic that has persisted seasonally since 2022 linked to the migration of waterfowl serving as reservoirs of the virus.
Attempting to eradicate a seasonally and regionally endemic disease is a futile exercise. Reliance on biosecurity is inadequate as a protective measure given the evident aerogenous spread of infection. The alarming increase in the incidence rate of bovine influenza-H5N1 in dairy herds especially in the Central Valley of California attests to the impotence of control measures attributed to deficiencies in biosecurity. EGG-NEWS has also commented on the inadequate protection of workers with evident susceptibility to infection of epithelial cells of the conjunctiva and mucosa of the upper respiratory tract.
The impact of HPAI on the egg production segment extends beyond expenditure on control by APHIS and the extensive losses experienced by flock owners. Consumers now bear the brunt of the disease through escalation in the price of eggs. In 2022, it is estimated that with an average $2 per dozen increase in price, consumers paid $15 billion more for their eggs than during the previous year when flocks were maintained at a level that was in balance with demand. It is now apparent that a similar situation will pertain in 2024.
It is absolutely necessary for APHIS to backtrack on promoting biosecurity and stamping out infected flocks. It is time to recognize recognize the regional and seasonal endemicity of avian influenza H5N1 and introduce vaccination for replacement pullets and even laying flocks at risk to create an immune population. This will reduce incident cases and lower the probability of the emergence of a mutant, zoonotic strain of avian influenza H5N1.
Sometime in the not too distant future USDA-APHIS, the egg and turkey segments of the poultry industry, Congress, public health agencies and consumer groups will have to face the existential question—Are the risks and the consequences of a human pandemic worth maintaining a proportion of the export volume of broiler leg quarters? The introduction of vaccination will not be a panacea. It will moderate the alarming and costly incidence rate in poultry. Above all creating an immune poultry population will provide a measure of security against emergence of a ‘swine flu’ or ‘Spanish Flu’ pandemic. Time is on the side of nature given large susceptible flocks and their concentration along major migratory flyways, coupled with the proclivity of single-stranded RNA viruses to undergo mutation.
*Lin, T., et al, A Single Mutation in Bovine Influenza H5N1 Hemagglutinin Switches Specificity to Human Receptors, Science doi:10.1126/science. ADT0180 2024