4 takeaways from Pennsylvania’s latest bird flu briefing

With avian influenza affecting everything from domestic poultry flocks to egg prices at the supermarket, state lawmakers in Harrisburg on Wednesday heard from several experts in veterinary medicine and influenza on how outbreaks of highly pathogenic avian influenza are affecting Pennsylvania – and what can be done to limit and contain the spread of the virus. 

According to the Centers for Disease Control and Prevention, in 2025, cases of avian influenza – also known as HPAI, H5N1, or bird flu – were detected in commercial poultry flocks in at least 10 Pennsylvania counties and in wild birds. However, the virus has not been detected in livestock in Pennsylvania, and no commonwealth residents have contracted it to date. 

Leaders from the University of Pennsylvania’s School of Veterinary Medicine and Perelman School of Medicine were in the state Capitol on Wednesday to inform lawmakers about the spread of H5N1 in North America and examine ways that the agricultural community and government entities can work together to better control the spread of avian influenza. 

Avian flu threat is ‘unlikely to dissipate’ this year

Dr. Andrew Hoffman, the dean of the University of Pennsylvania’s School of Veterinary Medicine, told state lawmakers that the threat of avian influenza is unlikely to go away anytime soon. 

“HPAI has not been stamped out in the United States,” Hoffman told House lawmakers on Wednesday. “Many new confirmed cases in commercial poultry recently in the commonwealth have underscored the urgency of combating this outbreak. Further, the virus appears to have adapted or sustained endemic infection in wildlife populations, making it unlikely to dissipate as a threat in this calendar year or anytime in the foreseeable future.” Hoffman said it would take a collaborative effort from experts in medicine and all levels of government to protect both animals and the public from highly pathogenic avian influenza. 

Louise Moncla, an assistant professor of pathobiology at Penn who tracks viral outbreaks, noted that the prevalence of HPAI in wild bird populations has made the disease more challenging to manage. Moncla told lawmakers that the spread of the virus among these populations carries several implications, including that migration can facilitate the disease’s spread over large geographic distances and from farm to farm, and that the virus may also start to mix with existing viruses within wild bird populations. 

“Because these viruses are now well established in wild birds, it means that these viruses can rapidly spread across geographic space, they can repeatedly spill over into domestic poultry, and they’re also mixing via this process called reassortment,” Moncla said.

Combating the spread of avian influenza

Hoffman said control of H5N1 depends on three key actions: tracking new cases of H5N1 in both animals and humans – along with their origins; monitoring changes to its ability to adapt and spread; and observing virus modifications that may make it more resistant to antiviral medications and vaccines.  

“We can’t let up on surveillance,” Hoffman said, adding that Penn is continuing to conduct diagnostic testing and surveillance of domestic and wild birds, and performing risk assessments on the disease’s potential to spread in humans. He added that the university is also doing public outreach and education about food safety and biosecurity measures that can limit the spread. 

Moncla affirmed that testing efforts are key to limiting the impact of HPAI outbreaks. “Strong testing, surveillance and outbreak response are really critical for outbreak mitigation – and this is an area that I think Pennsylvania is currently doing really, really well,” she said.

Vaccines for H5N1 that are currently in development could also be used to limit the spread in people who are at high risk for contracting the disease – particularly agricultural workers – as well as in poultry and cattle, said Scott Hensley, a professor of microbiology at Penn who is the principal investigator for the Penn Centers of Excellence for Influenza Research and Response. 

“I think that we’re at a point of this situation where we should consider, as a country, vaccinating people working with poultry, people working with cattle. I know that has been discussed on a national stage,” Hensley said. 

When asked about the potential harmful impacts of H5N1 vaccines on humans, Hoffman looked to downplay worries. “The quick answer to that is: We don’t know – and I think that it’s really important to consider the safety of food and everything that we’re putting into the food system,” he said. “There are many vaccines that are issued to dairy cattle, swine and poultry at this moment that have been utilized safely and to protect the agricultural industry …We’re consuming food products that have received vaccines and, so far, those have been very safe products. The vaccine-related immune response and the products that you’re consuming have generally never been associated with human illness.”

Risk of human infection is ‘actually very low’

According to the Centers for Disease Control and Prevention, there have been 70 confirmed cases of H5N1 in humans in the U.S. to date, including one death in Louisiana. Pennsylvania has yet to record a human case of avian influenza.

Hensley stressed that the current risk of a human contracting H5N1 is low: “The bottom line is – today, as we stand here in February 2025 – your risk of H5N1 infection for the common person walking on the street is actually very low. Most of these infections are with humans that are interacting with these infected animals.”

That’s not to say the risk of human infection is zero. 

Hensley said that of the 70 human infections in the U.S., 41 have been in people who work with dairy cattle and 23 cases were in people who worked with infected poultry, highlighting how those who work directly with animals are at higher risk for contracting the virus. 

“The humans, the ones that are working closely with infected animals, those are the ones that are high-risk,” he said, noting that H5N1 viruses currently bind well to avian cells, but don’t bind as well to human cells. “But we know that that can change literally overnight, and I think we have to continue to invest in these H5 vaccines that could potentially be used if there’s a human pandemic.”

Federal funding decisions loom over response efforts

Hensley added that the current uncertainty over the future of federal funds – part of a push to review federal government spending by President Donald Trump’s administration – has researchers worried about losing access to resources to combat the spread of bird flu.

“We’re sweating a little bit,” Hensley told lawmakers on Wednesday. “My center – it’s about $10 million a year we get from federal spending. That goes away next month – guess what? The whole staff’s getting laid off. We don’t have money to pay them. So, doing the surveillance effort, sequencing, doing the basic science studies, trying to understand how mutations affect the ability to infect human cells, developing vaccines – that all goes away. I would be lying to you if I were to tell you that we aren’t all sweating. We’re really nervous to see some of the conversations on the federal level as far as it relates to funding the surveillance effort and vaccine effort.”