United States: The H5N1 avian influenza virus currently circulating on dairy and poultry farms in the United States has found a populace largely devoid of prior immunity, according to preliminary assessments by the Centers for Disease Control and Prevention (CDC).
Furthermore, ongoing reports indicate steady occurrences of outbreaks among dairy herds, alongside intermittent cases among poultry populations, according to CIDRAP News.
Serology evaluations conducted by the CDC were based on blood samples collected across all ten geographical regions of the US during two preceding flu seasons—2021-22 and 2022-23. These samples were tested against the H5N1 virus to determine antibody reactions. The findings indicated low antibody levels among both vaccinated and unvaccinated individuals, suggesting a widespread susceptibility should the virus evolve into a strain more adept at human-to-human transmission.
“This discovery is unsurprising given that A(H5N1) viruses have not yet widely circulated among humans and significantly differ from currently prevalent seasonal influenza A viruses,” remarked the CDC in its latest update on response efforts.
Despite these developments, the general risk to the public remains minimal, with only three documented cases of human infection linked to the dairy farm outbreaks, all involving individuals in close contact with cattle, as per CIDRAP.
In response to the escalating situation, federal health authorities have engaged CSL Seqirus to prepare bulk supplies of one of the two candidate H5 viruses, enough to produce 4.8 million doses. The CDC has endorsed this vaccine as effectively matched to the prevailing H5N1 strain.
On a global scale, the primary threat posed by the 2.3.4.4b clade of viruses appears to be to individuals who have encountered infected animals. In a parallel development, Finland’s health ministry has announced plans to distribute avian flu vaccines to groups at high risk of exposure, such as poultry farmers, fur-farm workers, and veterinarians, sourced through joint procurement with 15 European Union nations. The vaccine in question was developed by Seqirus UK, Ltd, CIDRAP reported.
Dairy herd outbreaks have surpassed a count of 100, with the virus also impacting additional poultry populations. The USDA’s Animal and Plant Health Inspection Service (APHIS) has confirmed six new H5N1 outbreaks among dairy herds, elevating the US total to 102. The latest cases include five farms in Colorado and one in Iowa.
Moreover, the Iowa Department of Agriculture and Land Stewardship has reported three additional outbreaks in dairy herds—two in Sioux County and one in Plymouth County—while Minnesota has recorded another outbreak among commercial poultry, affecting a turkey farm housing 33,100 birds in Stearns County.
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