Experts tell Pennsylvania joint committee H5N1 remains entrenched in wild birds, threatens poultry and dairy; urge surveillance and targeted vaccination

HARRISBURG, Pa. — University of Pennsylvania infectious-disease and veterinary experts told a Feb. 24 joint hearing of the Pennsylvania House Agriculture and Rural Affairs Committee and the Health Committee that highly pathogenic avian influenza (HPAI) H5N1 is now established in wild birds across North America, continues to spill into domestic poultry and dairy cattle, and has caused a small number of human infections. They recommended sustaining and expanding surveillance, tightening biosecurity on farms, and considering targeted vaccination for workers and certain animal populations.

Why it matters: The panel said the outbreak has cost U.S. agriculture heavily and remains a public‑health concern because the virus keeps evolving. That continuing viral circulation raises the chance of mutations that could increase human transmissibility, the experts said.

University of Pennsylvania Dean Andrew Hoffman, representing Penn Vet, summarized the briefing’s goals—tracking cases, monitoring viral changes and preparing vaccines—and warned that the virus has “devastating consequences to poultry.” Dr. Hoffman said multi‑sector collaboration among academic, state and federal partners is essential to slow the outbreak.

Louise Moncla, assistant professor of pathobiology at the University of Pennsylvania School of Veterinary Medicine, described viral “family trees” used to trace introductions and spread. Moncla said genomic evidence shows H5N1 entered North America from migrating wild birds and then established sustained circulation in wild-bird reservoirs. That persistence means repeated reintroductions into farms and greater geographic spread.

“Because these viruses are now well established in wild birds, it means that these viruses can rapidly spread across geographic space,” Moncla said. She identified the D1.1 genotype as the currently dominant lineage in wild birds and linked it to recent poultry outbreaks and to severe human cases reported in British Columbia and Louisiana.

Lisa Murphy, professor of pathobiology and resident director of Penn Vet’s New Bolton Center, described laboratory and field testing in Pennsylvania. New Bolton Center and the state’s diagnostic network have run tens of thousands of tests: Penn Vet reported more than 20,000 samples at New Bolton Center alone and noted Pennsylvania’s routine bulk‑tank milk and individual‑cow testing. Murphy said Pennsylvania’s labs participate in the National Animal Health Laboratory Network and forward non‑negative results to the National Veterinary Services Laboratory for confirmation.

Scott Hensley, professor of microbiology and director of Penn’s Center of Excellence for Influenza Research and Response, summarized human infection data and vaccine work. Hensley said 69 human infections had been confirmed in the United States as of the briefing, most among people with animal exposure, and that two severe North American human cases showed the same mutation—at hemagglutinin residue 226—that laboratory studies indicate can increase the virus’s ability to bind human airway cells.

“We are at a point of this situation where we should consider as a country vaccinating people working with poultry, people working with cattle,” Hensley said, arguing the dual benefit of reducing human risk and lowering viral burden in animals. Hensley noted that mRNA vaccines under development produce promising protection in animal models and that Penn has begun studies of vaccine responses in cattle.

Committee members asked about international responses, the difference between vaccinating layers and broilers, the safety of vaccinated animal products, PCR testing reliability and whether Pennsylvania should incentivize smaller layer operations. Panelists said vaccination has been used in other countries’ poultry sectors with mixed results; pasteurization inactivates the virus in milk and the food supply is safe when pasteurized; and PCR positives have been repeatedly confirmed by the national reference laboratory.

The experts repeatedly emphasized that reducing total circulating virus—by surveillance, better farm biosecurity, testing and, where appropriate, vaccination—was the primary way to reduce the chance of a viral mutation that could enable sustained human‑to‑human spread. They also warned that once HPAI becomes established in wildlife and enters cattle herds, control is substantially harder.

The hearing closed with lawmakers asking the panel to provide a written series of recommended next steps and noting concern about current and potential federal funding gaps for surveillance and research. Panelists said state investments and continued federal support will be needed to maintain laboratory staffing, sequencing and vaccine-development work.

The committees did not take formal action during the hearing. Follow‑up steps discussed included continuing mandatory testing of bulk milk where applicable, maintaining laboratory capacity and considering targeted vaccination policies for high‑exposure workers and certain animal categories.