Enlarge / A cow grazes in a field at a dairy farm on April 26, 2024, in Petaluma, California. (credit: Getty | Justin Sullivan)

The outbreak of H5N1 bird flu in US dairy cows has now spread to three herds in California, the largest milk-producing state in the country, with around 1.7 million dairy cows, federal and state health officials have confirmed.

Fourteen states and 197 herds have now been affected by the unprecedented outbreak in dairy cows, which was first confirmed by federal health officials on March 25.

In a statement, the secretary of the California Department of Food and Agriculture, Karen Ross, said the spread of the virus to California was not unexpected. "We have been preparing for this possibility since earlier this year when [Highly pathogenic avian influenza or HPAI] detections were confirmed at dairy farms in other states," Ross said. "Our extensive experience with HPAI in poultry has given us ample preparation and expertise to address this incident, with workers’ health and public health as our top priorities."

Enlarge (credit: Getty | Justin Sullivan)

The US government will pay Moderna $176 million to develop an mRNA vaccine against a pandemic influenza—an award given as the highly pathogenic bird flu virus H5N1 continues to spread widely among US dairy cattle.

The funding flows through BARDA, the Biomedical Advanced Research and Development Authority, as part of a new Rapid Response Partnership Vehicle (RRPV) Consortium. The program is intended to set up partnerships with industry to help the country better prepare for pandemic threats and develop medical countermeasures, the Department of Health and Human Services said in a press announcement Tuesday.

In its own announcement on Tuesday, Moderna noted that it began a Phase 1/2 trial of a pandemic influenza virus vaccine last year, which included versions targeting H5 and H7 varieties of bird flu viruses. The company said it expects to release the results of that trial this year and that those results will direct the design of a Phase 3 trial, anticipated to begin in 2025.

Enlarge (credit: Getty | Yui Mok)

The strain of H5N1 bird flu isolated from a dairy worker in Texas was 100 percent fatal in ferrets used to model influenza illnesses in humans. However, the virus appeared inefficient at spreading via respiratory droplets, according to newly released study results from the Centers for Disease Control and Prevention.

The data confirms that H5N1 infections are significantly different from seasonal influenza viruses that circulate in humans. Those annual viruses make ferrets sick but are not deadly. They have also shown to be highly efficient at spreading via respiratory droplets, with 100 percent transmission rates in laboratory settings. In contrast, the strain from the Texas man (A/Texas/37/2024) appeared to have only a 33 percent transmission rate via respiratory droplets among ferrets.

"This suggests that A/Texas/37/2024-like viruses would need to undergo changes to spread efficiently by droplets through the air, such as from coughs and sneezes," the CDC said in its data summary. The agency went on to note that "efficient respiratory droplet spread, like what is seen with seasonal influenza viruses, is needed for sustained person-to-person spread to happen."

Enlarge / Suri alpacas on a farm in Pennsylvania. (credit: Getty | Susan L. Angstadt)

Four backyard alpacas in southern Idaho have tested positive for highly pathogenic avian influenza (HPAI) H5N1, marking the first time bird flu has been detected in members of the fleecy camelid family, according to the US Department of Agriculture.

On Tuesday, the USDA announced that the agency's National Veterinary Services Laboratories confirmed the infection on a farm in Jerome County on May 16. While the infections are a first for the spitting llama relatives, the USDA said they weren't particularly surprising. The alpacas were in close contact with HPAI-infected poultry on the farm, which were "depopulated" this month. Of 18 alpacas on the affected farm, only four were found to be infected. There were no deaths documented, according to a report the USDA submitted to the World Organization for Animal Health.

Genomic sequencing indicates that the H5N1 virus infecting the alpacas (B3.13) matches both the virus currently circulating among US dairy cows and the virus that infected birds on the farm.

Enlarge / Fresh raw milk being poured into a container on a dairy farm on July 29, 2023, in De Lutte, Netherlands. (credit: Getty | Pierre Crom)

Despite the delusions of the raw milk crowd, drinking unpasteurized milk brimming with infectious avian H5N1 influenza virus is a very bad idea, according to freshly squeezed data published Friday in the New England Journal of Medicine.

Researchers at the University of Wisconsin-Madison squirted raw H5N1-containing milk from infected cows into the throats of anesthetized laboratory mice, finding that the virus caused systemic infections after the mice were observed swallowing the dose. The illnesses began quickly, with symptoms of lethargy and ruffled fur starting on day 1. On day 4, the animals were euthanized to prevent extended suffering. Subsequent analysis found that the mice had high levels of H5N1 bird flu virus in their respiratory tracts, as well their hearts, kidneys, spleens, livers, mammary glands, and brains.

"Collectively, our data indicate that HPAI [Highly Pathogenic Avian Influenza] A(H5N1) virus in untreated milk can infect susceptible animals that consume it," the researchers concluded. The researchers also found that raw milk containing H5N1 can remain infectious for weeks when stored at refrigerator temperatures.