Study finds widespread H5N1 infection in black vultures

Bird flu appears to be far more entrenched in black vultures than many wildlife and veterinary observers expected. A new Scientific Reports paper from University of Georgia investigators found highly pathogenic avian influenza A(H5N1) in 113 of 134 dead black vultures examined from 2022 to 2023, or 84.3%, across seven southeastern states. The authors conclude that year-round mortality in 2022 may have been maintained by conspecific scavenging, raising concern that black vultures can sustain transmission beyond the classic migratory waterfowl window. (nature.com)

That fits into a broader shift in how H5N1 is behaving in wild birds. Johanna Harvey’s new Wildlife Monographs analysis argues that circulating highly pathogenic avian influenza viruses now show an expanded susceptible host range and higher transmission rates, with migration, host demographics, and species interactions shaping spread in ways that matter for both conservation and public health. Harvey’s review describes the current wave as affecting hundreds of avian species and argues that the dominant strain has an elevated ability to infect hosts, helping explain why species outside the traditional waterfowl focus are drawing more attention. (uri.edu)

The black vulture paper adds unusually detailed pathology and field observations to that bigger picture. The study documented 55 distinct mortality events, with many reports involving clusters of dozens of birds and some events exceeding 100 affected vultures. Most infected vultures were found dead or died shortly after discovery, and common lesions included enlarged, mottled spleens and livers with severe necrosis. The authors said the digestive tract findings, together with field observations, support ingestion of high viral doses as an important route of infection, which makes ecological sense in a species that feeds communally on carrion, uses dense roosts, and readily exploits landfills and other human-modified environments. (nature.com)

University of Georgia’s public summary put the scale in more concrete terms for a broader audience: the sampled birds may represent “tens or hundreds of thousands of black vultures,” according to lead author Dr. Nicole Nemeth, although that estimate is an extrapolation rather than a direct census count. UGA also highlighted a possible silver lining from earlier work: about half of infected vultures may survive, and some survivors had antibodies, suggesting at least partial population-level resilience even as transmission remains intense. (news.uga.edu)

Researchers also stressed that the concern isn’t limited to one scavenger species. Nemeth said sustained transmission creates more opportunities for viral change, while co-author Rebecca Poulson noted the diversity of avian influenza viruses still circulating and mixing in wildlife. That doesn’t mean vultures are currently driving a new human threat; CDC continues to assess the current risk to the general public as low. But CDC also says people usually become infected after close, unprotected exposure to infected birds or other animals, which keeps veterinarians, wildlife staff, rehabilitators, and others handling carcasses or sick birds in a higher-risk category than the general public. (news.uga.edu)

Why it matters: For veterinary professionals, this study is a reminder that H5N1 surveillance and clinical awareness can’t stay centered only on waterfowl and poultry. Black vultures may be functioning as a visible indicator of wider environmental circulation and as a self-perpetuating transmission node among scavengers. That has implications for differential diagnoses in wildlife cases, necropsy precautions, clinic and rehab intake protocols, communication with livestock clients about carcass management and wildlife contact, and conversations with pet parents who may find dead birds on their property. It also underscores the One Health overlap between wildlife disease ecology, poultry protection, livestock biosecurity, and occupational exposure. APHIS continues to maintain national wild bird detection reporting and surveillance planning, reflecting how central wildlife monitoring has become to the U.S. response. (nature.com)

What to watch: The next questions are whether ongoing surveillance shows persistent off-season circulation in vultures, whether similar patterns emerge in other obligate or near-obligate scavengers, and whether population impacts become measurable over time. The paper’s authors called for continued monitoring of black vultures to assess ecological effects, and the broader host-dynamics work suggests wildlife agencies may need to keep widening the list of species that matter for forecasting H5N1 spread. (nature.com)