It seems that there might have been one other spillover of H5N1 hen flu virus from wild birds into dairy cattle. The Arizona Division of Agriculture introduced Friday that it had discovered the virus in milk from a herd of cows in Maricopa County, which accommodates the state capital, Phoenix.
That is the primary detection of H5N1 in dairy cows in Arizona, making it the seventeenth state wherein affected cows have been discovered. Practically 970 herds have examined constructive because the outbreak was first recognized in late March 2024.
The Arizona detection occurred as a part of the U.S. Division of Agriculture’s Nationwide Milk Testing Technique, which samples bulk milk searching for presence of H5N1 viruses. Final week, USDA and Nevada’s Division of Agriculture introduced a detection there of H5N1 in dairy herds.
Because it was first found that hen flu viruses had been infecting cows and spreading amongst herds, it was thought that the entire detections had been related — that there had been a single soar of the H5N1 virus into cows, in both late 2023 or early 2o24, possible in Texas. That evaluation was based mostly on ongoing evaluation of the genetic sequences of the viruses, which belong to a household of H5N1 referred to as clade 2.3.4.4b, genotype B3.13.
USDA milk testing reveals completely different pressure of H5N1 hen flu in Nevada dairy herds
However the discovery of the virus in milk from Nevada herds in early January — outcomes that had been solely launched final week — confirmed {that a} completely different model of the virus was liable for these infections. That virus belonged to the identical clade, however was of the D1.1 genotype, a model of the virus liable for a extreme an infection of a youngster in British Columbia, Canada in November, and the demise of an individual who owned a yard poultry flock in Louisiana in January.
The virus remoted from the milk of the Arizona herd was additionally a D1.1 virus, however apparently a unique model of it.
“This detection of avian influenza is per a D1.1 genotype and unrelated to the latest Nevada detection of this virus,” the Arizona assertion stated. “This D1.1 genotype bears no options that will make it extra prone to infect people.”
When the Nevada detection was made public, flu scientists warned that extra spillovers into cows had been possible, given how prevalent H5N1 is in wild birds throughout the nation. However Arizona’s announcement nonetheless got here as a shock.
“I undoubtedly thought there can be extra jumps discovered by milk testing. However I’ve to admit I didn’t assume it might occur fairly so quick, nor in my very own yard as I seemed north, over Maricopa County, to what’s taking place in Nevada!” Michael Worobey, an evolutionary biologist on the College of Arizona, informed STAT by textual content.
Previous to the outbreak in cows, the USA had solely ever detected one human H5N1 an infection, in a person who was concerned in culling contaminated poultry in Colorado. That an infection occurred in 2022.
However over the previous 12 months, there have been 68 confirmed human circumstances, and a quantity extra the place state laboratories have seen a constructive end result however further testing carried out on the Facilities for Illness Management and Prevention couldn’t affirm the case, typically due to low ranges of viral materials or degradation of the pattern throughout transport. The vast majority of these circumstances have occurred in folks with direct contact with dairy cows or poultry flocks, that are additionally inclined to contracting the virus from wild birds.
