Study links black vultures to year-round H5N1 circulation: full analysis

A new University of Georgia study is putting black vultures in sharper focus in the H5N1 story. Published in Scientific Reports, the paper found that more than four in five dead black vultures examined in 2022 and 2023 tested positive for highly pathogenic avian influenza, with the authors warning that the real toll is likely much larger and that the species’ scavenging behavior may help keep the virus circulating year-round. (news.uga.edu)

That matters because black vultures weren’t initially the headline species in North America’s clade 2.3.4.4b outbreak. Since H5N1 arrived on the continent in late 2021, surveillance has centered heavily on waterfowl, poultry, and later dairy cattle and human spillover events. But wildlife agencies were seeing black vulture die-offs early in the outbreak, including more than 100 deaths reported in Maryland in 2022, while Florida documented ongoing mortality in roosts where vultures were observed scavenging infected carcasses. (news.maryland.gov)

In the new study, researchers analyzed 134 dead black vultures collected across seven states in 2022 and 2023. More than 84% tested positive for H5N1, and the paper describes both biological susceptibility and ecological vulnerability: black vultures feed indiscriminately on carrion, gather in dense social groups, and may consume infected members of their own species. According to UGA’s summary, those behaviors appear to extend transmission beyond the typical bird flu season, creating more opportunities for the virus to persist and evolve, even though the researchers did not report evidence that a more dangerous variant has emerged in vultures. (news.uga.edu)

The study also builds on a growing body of evidence that black vultures may be unusually important in H5N1 ecology. A 2025 Journal of Wildlife Diseases report on 2022 outbreaks concluded that infections likely began through scavenging infected bird carcasses and may then have been maintained within vulture populations through conspecific scavenging. Florida wildlife officials have described black vultures as the species most commonly diagnosed with HPAI in the state during part of the 2022 outbreak, reinforcing the idea that this is not an isolated signal. (pubmed.ncbi.nlm.nih.gov)

UGA researchers framed the concern in both ecological and One Health terms. Nicole Nemeth said diminished vulture populations can leave more carcasses on the landscape, a change associated with increased disease risks for people, wildlife, and domestic animals. Co-author Rebecca Poulson also pointed to the broader virology concern: continued circulation and mixing of avian influenza viruses in wildlife increases the diversity of viruses that North American species may face. Separately, APHIS says wild bird surveillance is meant to provide early warning for poultry and other populations of concern, underscoring why a scavenger species with broad geographic range could matter operationally, not just academically. (news.uga.edu)

Why it matters: For veterinarians, especially those in mixed animal, poultry-adjacent, wildlife, shelter, and emergency settings, this study is a reminder that H5N1 risk doesn’t sit neatly within traditional seasonal or species boundaries. Black vultures often overlap with livestock operations, roadkill corridors, landfills, and peri-urban spaces. That means carcass handling protocols, exclusion efforts around feed and disposal areas, staff PPE decisions, and client guidance about avoiding dead birds all stay relevant even outside peak migratory windows. It also reinforces the value of close coordination with state wildlife agencies, agriculture departments, and public health partners when unusual bird deaths appear near farms or communities. (news.maryland.gov)

The public health backdrop is still relatively reassuring, but not static. CDC says H5 surveillance and human monitoring continue under a streamlined reporting cadence, and PAHO reported 75 human H5N1 infections and two deaths across the Americas from April 2022 through March 9, 2026, with no new cases since late 2025. Even so, the vulture findings support the idea that wildlife reservoirs and bridge species remain central to risk management, particularly where veterinary teams may be the first to spot unusual illness or mortality patterns. (cdc.gov)

What to watch: The next questions are whether expanded surveillance finds similar year-round patterns in other scavengers, whether sequencing identifies meaningful viral changes in vulture-associated outbreaks, and whether regulators and wildlife agencies update guidance on carcass disposal, farm biosecurity, or wildlife rehabilitation in response to these findings. (nature.com)