NVSL Released AZ D1.1 (We Think), but That's Just the Half of It...

8 B3.13 Poultry Samples Came from Somewhere and No Infected Flocks were Reported from Known Infected Dairy States...

My maternal grandfather was a pithy old German, and I’m coming to reflect his attitude! When he saw something of little value, his first reaction, much to the chagrin of my Mennonite-bred grandmother, was: “Worthless as teats on a boar…” Release of H5N1 sequence data with very limited metadata several weeks after isolation comes very close to that definition! Researchers and analysts are left to piece together what they can from information that ought to be in the public realm. Regardless, the policy is not going to change in the short term, and analysts do an amazing job of piecing together information based on known sequences and genomic relationships to make best estimates of phylogenetic epidemiological relationships. In some cases these genomic relationships can confirm rumors or hunches.

NVSL released 10 poultry outbreak sequences last Friday - 8 were genotype B3.13 and 2 were D1.1, with those 2 rumored to match the D1.1 sequences “possibly” isolated from AZ dairy cattle earlier in 2025. That would lend credence to a rumor that was circulating internally in the poultry community that the AZ H5N1 infection was “dairy origin” from a neighboring farm.

It’s extremely disappointing that USDA and the Arizona Department of Agriculture have refused to disclose this information to the public, including any plans or results from testing of neighboring dairy farms. Additionally, Arizona Public Health has been silent on any activities related to worker protection or increased surveillance in the area. I don’t expect anything from CDC/HHS at this point; however, I’d hope state officials would take their roles seriously when the federal government seems paralyzed. This poultry event has been ongoing for nearly 4 weeks now since the first clinical signs and NAHLN lab diagnostics. The 4th infected AZ dairy herd milk sample was confirmed on May 7th (without comment).

I find it really hard to fathom that farm workers and responders have all been free of symptoms of URI and conjunctivitis. D1.1 has a history of human crossover in other states. it really needs to be watched. Is anyone being monitored (any from the prying eyes of ICE)? Why are the State’s Governor and 2 Senators (all Democrats) not on top of this? I hope there is a lot more public communications regarding this outbreak and response by the end of the week.

H5N1 B3.13 in Poultry-Infected Dairy Herd Sentinel Detection

Let’s move on to the 8 B3.13 genotype isolates that were also released last Friday. Here are states that have had commercial flock outbreaks since March 15; one or more of them is likely to be sources of the 8 isolates:

Without metadata, we don’t know which state or states was the source of the samples; however, NONE of these states have reported any infected dairy herds this year! None of them have disclosed that they had a B3.13 outbreak in a poultry herd or stated that testing of adjacent dairy herds might be indicated. If anyone tested dairy herds, it was done quietly, and results were negative. We may have some idea of possible states affected when the 8 sequences are phylogenetically compared to known dairy viruses (work now underway).

Many states claim that the National Milk Testing Strategy (NMTS) is being implemented, but details are extremely limited. Poultry outbreaks show H5N1 B3.13 remains “out there” in mid-continent U.S.; we really don’t yet know where and how much because we just aren’t testing! H5N1 in dairy is not a confidential state vet/dairy industry problem to be managed privately. Infected poultry, cats, and hospitalized humans will eventually catch up with that strategy.

Finally, the track record seems to show that dairy spillover infections may be resistant to control through traditional HPAI biosecurity protocols (sorry Secretary Rollins…). I know that will be a controversial statement; my reasoning is that natural crossover between operations, especially high-biosecurity layer farms is less likely, and the B3.13 virus has not been shown to be carried by wildlife. Yet H5N1 seems to easily gain entry to large poultry populations from larger dairy populations.

Regardless of any of our preconceptions for crossover mechanics, I’d urge folks on the ground to really look for connections, not just associations. We all need more proof and less assumptions, more shown causation and less simple association. Epidemiology can become dubious when we repeatedly rely on preconceived notions or politically correct theories to explain spread.

My final comment and pet peeve is to take into account total viral load and outbreak timing. Load is decreasing by the time the chickens start dying in a section of a building or on a premises. The same is true with dairy herds; respiratory viral shed and viremia peak early. Milk virus may peak later, but how much of it ends up aerosolized or infectious versus destroyed? High risk for spread occurs when viral shedding is high, i.e. early on. Often, that is before we have even diagnosed infection!

John