Minnesota reports one H5N1 detection in dairy; statewide monthly milk testing continues

Minnesota officials confirmed one detection of highly pathogenic avian influenza (H5N1) in a dairy herd and said they will continue statewide monthly bulk-tank milk surveillance while moving to scale laboratory capacity and vaccine access.

The dairy detection, reported in March, was a low‑level positive on a follow‑up test, and state investigators said sequencing may not be possible because the sample cycle threshold values were high. “When you start to get to 35 and above, those are either waxing and waning or it's a new infection starter,” said Dr. Brian Hayes, executive director of the Minnesota Board of Animal Health, describing laboratory limits for sequencing and the implication for determining whether an infection is new or persistent.

Why it matters: The detection underscores a shift for animal health authorities from episodic outbreaks toward ongoing surveillance in multiple species. State and federal agencies are treating H5N1 as a multiyear, multi‑species challenge that affects commercial poultry, backyard flocks and dairy cattle and has human exposure implications.

What officials described - Milk testing program: Nikki Neazer, director of the Dairy and Meat Inspection Division at the Minnesota Department of Agriculture, said the state’s program aims to sample every dairy cattle farm roughly once per month. “Our goal is really to sample all of our cow farms,” Neazer said, and the first full month of sampling reached more than 1,400 unique farms. Samples are collected as sub‑samples from plants’ regulatory screening flows and shipped to the veterinary diagnostic laboratory for PCR testing. - The positive dairy herd: State investigators said the initial farm that tested positive showed high cycle‑threshold (CT) values on PCR (in the mid‑30s), meaning low levels of detectable viral material. That pattern makes sequencing—and therefore identifying whether the virus is a carryover from an earlier event or a new introduction—difficult or sometimes impossible. - Human monitoring and PPE: A Minnesota Department of Health representative reported no human detections in Minnesota tied to this dairy detection but said six people associated with the recent positive dairy herd remain in monitoring. “We currently have 6 people in monitoring associated with the recent positive dairy farm,” the MDH speaker said, and the department has been supplying personal protective equipment to at‑risk workers. - Vaccines: Hayes said Minnesota supports rapid access to vaccines if USDA and manufacturers can reliably supply them. He told the board that some modified‑live and killed vaccines for poultry respiratory diseases have been approved for import or conditional use and that distribution will be prioritized by manufacturers; the state is encouraging USDA to secure extended authorizations so manufacturers can plan production lead times.

Laboratory capacity and logistics State officials described a supply and logistics chain that includes industry intake laboratories, centralized section‑6 labs and the Minnesota Veterinary Diagnostic Laboratory for confirmatory testing. Officials used MTM (molecular transport medium) tubes to stabilize subsamples and described procedures designed to tolerate short shipping delays. “We have essentially stabilized the virus in those samples,” Neazer said, explaining why the diagnostic lab can accept samples even if overnight shipment windows slip.

Outstanding questions and next steps Officials said the state will continue weekly surveillance of high‑risk populations, maintain an incident management team for H5N1 response, and pursue sequencing where CT values permit. They also said USDA funding ultimately covers much of the testing effort but that the state used emergency funds briefly while federal cooperative agreements were finalized.

Context and caveats State leaders cautioned that low PCR signals (high CTs) limit what sequencing can reveal, and they declined to speculate about whether any single detection represents a persistent farm infection or a new wild‑bird introduction unless genomic evidence is available. The detection prompted quarantine and follow‑up testing at the affected premises; the state said milk from positive herds is handled through normal pasteurization processes and is not withheld from the food supply when pasteurized.

Looking ahead: Neazer said Minnesota will continue monthly farm‑level milk testing through at least June and then reassess frequency based on results and national guidance. Hayes and other officials said they will push for vaccine availability, extend outreach to producers on biosecurity, and coordinate with human health partners on worker protection.