Conservation Bio: Emerging threat of avian influenza to the world's vultures - South Korea Study On HPAI in Vulture - San Francisco Raptors

[Michael Coston]

Conservation Bio: Emerging threat of avian influenza to the world's vultures​

Black Vulture - Credit Wikipedia


#19,307

Of the 19,631 entries in the USDA's Detections of Highly Pathogenic Avian Influenza in Wild Birds - which has only been intermittently updated in 2026 - 1215 (6.2%) are listed as vultures.

Other raptors and scavenger birds on the list include eagles (n=990), hawks (n=1010), Owls (n=764) and California Condors (n=22). But these lists are far from complete

Three and a half years ago, (Apr 8th, 2023) the U.S. Fish & Wildlife Service issued a statement stating that HPAI Was Confirmed As Cause Of Death For 3 California Condorsfound in Northern Arizona.

Considered a critically endangered species with a population of ≈ 560 birds today - the California Condor nearly went the way of of the dodo in the early 1980s, when its population declined to just over 20 (in the wild) due to the combined effects of DDT, lead poisoning and a loss of habitat.

As scavengers, Condors feed almost exclusively on carrion, which increasingly runs the risk of being infected with HPAI H5 (see USDA Mammalian HPAI Infection List). Within days, the number of Condor deaths rose sharply.

HPAI UPDATE

(Excerpt)

As of April 17, 2023, 20 condors have died in the Arizona-Utah flock; HPAI has been confirmed for 10 of those condors. Eight birds were captured and brought in for supportive care. Four of those condors died shortly thereafter and are included in the total of 20 deceased birds. Four condors are still receiving supportive care and have shown improvement. Learn more about HPAI.

While an emergency vaccination program was initiated in the fall of 2023, and more than 200 birds were eventually vaccinated, the carnage visited upon scavenger birds by H5N1 has continued.

While not every bird that gets infected dies (see Preprint: Exposure & Survival of Wild Raptors During the 2022-2023 Highly Pathogenic Influenza A Virus Outbreak), the virus's toll on avian populations around the world has been enormous.

Over the past few years we've looked at a number of papers from the tag-team of Pablo Plaza & Sergio A. Lambertucci (often in collaboration with Andrea Santangeli), including:

ISIRV: Update on H5N1 Panzootic: Infected Mammal Species Increase by Almost 50% in Just Over a Year

Travel Medicine & Inf. Dis.: Differences Between Influenza H5N1, A/H1N1 2009, and SARS-CoV-2 in a Pandemic Risk Scenario

Nature Reviews: The Threat of Avian Influenza H5N1 Looms Over Global Biodiversity

Travel Med. & Inf. Dis.: Pacific and Atlantic Sea Lion Mortality Caused by HPAI A(H5N1) in South America

EID Journal: Recent Changes in Patterns of Mammal Infection with Highly Pathogenic Avian Influenza A(H5N1) Virus Worldwide

Last week they published the following letter (excerpts below) in Conservation Biology. Follow the link to read it in its entirety.

Emerging threat of avian influenza to the world's vultures

Jon Morant, Andrea Santangeli, Pablo Plaza, Sergio A. Lambertucci
First published: 19 August 2026
https://doi.org/10.1111/cobi.70372Digital Object Identifier (DOI)
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Article impact statement: Five action areas need to be implemented across continents to address the potential impact of H5N1 on world's vulture populations.

Vultures are among the most threatened bird groups globally (Buechley & Şekercioğlu, 2016), yet they provide invaluable ecosystem services that support human well-being (Santangeli et al., 2024). At least 16 of 23 vulture species are of conservation concern worldwide, largely owing to toxicosis and other anthropogenic threats (Buechley & Şekercioğlu, 2016). The current panzootic caused by highly pathogenic avian influenza virus (H5N1) (hereafter H5N1) (Lambertucci et al., 2025) could represent a catastrophic addition to this threat mix, magnifying already steep population declines. In fact, globally, several important vulture hotspots are under threat from the intensive spread of this pathogen (Figure 1).

(SNIP)

We call upon conservationists and wildlife managers to adopt a comprehensive, multilayered approach to mitigating H5N1 risks in vultures, prioritizing five key action areas that balance immediate fieldwork situations with broader population resilience.

First, there is an urgent need for intensive medium- to long-term population monitoring in geographic regions impacted by the current H5N1 panzootic (Figure 1); this monitoring should be coupled with targeted epidemiological surveillance and seroprevalence studies in vulture communities to evaluate immunological status and improve knowledge of how H5N1 affects their populations beyond acute mortality events. This action is especially relevant for sites where information on vulture mortality due to H5N1 remains limited. Second, we advocate for the continuous evaluation of the potential need for vaccination campaigns for specific and emerging cases where populations face severe risk and logistical conditions allow (Katzner et al., 2025; Larson 2026).

Third, carcass management must be carefully adapted to local socioeconomic contexts; managers should prioritize preventing the use of suspected or H5N1-infected carcasses at feeding stations, mirroring existing safe carcass protocols used to exclude toxic pharmaceuticals in vulture safe zones (VSZs). Ensuring the provision of H5N1-free carcasses from both domestic and wild sources is crucial to reducing viral transmission at supplementary feeding stations (i.e., vulture restaurants) (Santangeli et al., 2025), which often attract large aggregations of obligate and facultative scavengers (Brink et al., 2020; Cortés-Avizanda et al., 2016). Rapid molecular testing protocols (such as rRT-PCR using freeze-dried reagents; Takekawa et al., 2011) and the systematic removal of infected carcasses (Gold et al., 2026) could be valuable interventions, although we recognize that their availability, cost, and sensitivity may represent important barriers to their implementation in many regions.

Fourth, we recommend strictly following handling protocols for vultures during fieldwork (e.g., tagging, morphometry, and health surveys) in accordance with H5N1 biosecurity guidelines to minimize transmission risk among individuals and species. Finally, given the diversity of socioeconomic and governance contexts in the countries across the vulture's range, we urge regional conservation and health bodies, such as the International Union for Conservation of Nature (IUCN) and the World Organisation for Animal Health (WOAH), to develop and promote context-specific action plans that prioritize these feasible, locally adapted interventions.

This pathogen could represent the final threat to some vulture populations; therefore, tackling the five action areas outlined above is urgent. Crucially, these measures must not be pursued in isolation; their integration into coordinated, transboundary frameworks is essential to address the full geographic and ecological scope of the crisis.

The current H5N1 panzootic is occurring across all continents where vultures occur, concomitantly with other threats affecting these species. Coordinated and transboundary plans that embed these actions into shared governance structures are urgently needed to address this dangerous epidemiological scenario, which could decimate vulture populations, as has occurred with other avian groups globally.

(Continue . . . )

In early 2025, in Nature Reviews: The Threat of Avian Influenza H5N1 Looms Over Global Biodiversity, we looked at the massive, and often underappreciated, impact of HPAI H5 on both avian and mammalian wildlife around the globe.

While I can't tell you precisely what negative impacts the loss of a Billion+ wild and captive birds, hundreds of thousands of marine mammals - or unfathomable numbers of peridomestic mammals - might have on our human society, one thing is certain.

We are well on our way towards finding out.

https://afludiary.blogspot.com/2026/08/conservation-bio-emerging-threat-of.html

 

[Michael Coston]

Transb. & Emerg. Dis.: Genomic and Clinicopathological Characterization of a Reassortant HPAI H5N1 (Clade 2.3.4.4b) in an Endangered Cinereous Vulture (Aegypius monachus) in South Korea, 2026​

Transboundary and Emerging Diseases, Volume: 2026, Issue: 1,
First published: 18 August 2026, DOI: (10.1155/tbed/2623621)

#19,308



Yesterday, in Conservation Bio: Emerging threat of avian influenza to the world's vultures, we looked - in broad terms - at the current and potential future impact of HPAI H5N1 on raptors and other scavenger birds.

Today we've a study - published last week in Transboundary and Emerging Diseases - which looks at one specific investigation into an H5N1-infected endangered Cinereous Vulture recovered in South Korea earlier this year.

While hardly a new finding (see Cell: The Neuropathogenesis of HPAI H5Nx Viruses in Mammalian Species Including Humans), once again we see strong evidence of neurological involvement in this recovered vulture; in clinical presentation, histopathological findings, and in high titers of the virus found in brain tissue.

This is a topic we've looked at often, most recently last month in Viruses: First Ecuadorian Pediatric Case of Multisystem and Neurological Involvement Associated with Influenza A—H5N1 Virus—Case Report, and before that, in last May's QJM: Avian Influenza in Humans: Virology, Transmission, and Clinical Priorities.

This study also found that the HPAI H5N1 virus recovered from the vulture was a reassortant (see graphic at top of blog). Its HA, NA, and M gene segments closely resembled a G10-like East Asian H5N1 virus which circulated circa 2022–2023, while its internal genes appear derived from multiple regional and flyway HPAI and LPAI viruses.

While much of this study is fairly technical, and will be primarily of interest to researchers, it is an excellent reminder of just how much hidden diversity there is in HPAI H5Nx in the wild, and that their evolution never stops.

I've only posted some excerpts. Those wishing a deeper dive will want to follow the link to read it in its entirety.

Genomic and Clinicopathological Characterization of a Reassortant HPAI H5N1 (Clade 2.3.4.4b) in an Endangered Cinereous Vulture (Aegypius monachus) in South Korea, 2026

Chang-Gi Jeong, Seongwon Hwang, Taeyeong Jung, Su-Beom Chae, Tae-Nam Kim, Nchimunya Siamulonga, Serin Sim, Geonwoo Baek … See all authors
First published: 18 August 2026 https://doi.org/10.1155/tbed/2623621Digital Object Identifier (DOI)
Academic Editor: Fabian Lean

Abstract

Clade 2.3.4.4b highly pathogenic avian influenza viruses (HPAIVs) continue to circulate widely in East Asia and undergo frequent reassortment in wild birds. Raptors are regarded as spillover hosts that may be exposed through predation or scavenging, yet integrated clinicopathologic and genomic investigations in cinereous vultures remain limited.

Here, we describe a fatal H5N1 HPAIV infection in a cinereous vulture (Aegypius monachus) found in South Korea on January 17, 2026. On presentation, the cinereous vulture showed severe neurologic dysfunction, including inability to stand, right-sided head tilt with pathologic nystagmus, reduced oculocephalic and palpebral reflexes, and intermittent bilateral leg tremors. The cinereous vulture died within 2 days after rescue, and a complete necropsy was performed.

Hematologic and biochemical testing revealed marked heterophil predominance, severe lymphopenia, mild monocytosis, and globulin values near the upper end of the reference interval. An oropharyngeal swab tested positive for influenza A virus, and a virus isolate, designated A/Cinereous_Vulture/Korea/26-JBN47/2026(H5N1), was recovered in embryonated chicken eggs. Histopathology showed nonsuppurative encephalitis and necrotizing myocarditis, and influenza A nucleoprotein was detected immunohistochemically in neurons and cardiomyocytes.

Tissue real-time RT-PCR showed the lowest cycle threshold value in the brain. Whole-genome sequencing demonstrated that 26-JBN47 belonged to clade 2.3.4.4b and contained a polybasic HA cleavage site (PLREKRRKR/GLF). Segment-level phylogenetic analysis revealed a reassortant genome constellation comprising a maintained H5N1 backbone in HA, NA, and M; low PAIV (LPAIV)-associated but H5N1-incorporated PA and NP segments; flyway-associated PB2 and NS segments; and a PB1 segment phylogenetically linked to regional LPAIV lineages.

Molecular marker analysis identified multiple substitutions previously reported to be associated with receptor-binding properties, polymerase-related fitness, virulence, and host-response modulation, whereas canonical PB2 mammalian-adaptive markers were absent. These findings show that 26-JBN47 was a reassortant clade 2.3.4.4b H5N1 HPAIV associated with systemic disease and clinicopathological findings consistent with neurotropic and cardiotropic infection in a cinereous vulture. They also support the potential value of scavenging raptors as sentinels of local or regional HPAIV circulation involving reassortant viruses in East Asia.

(SNIP)

5. Conclusion

This study documents a fatal clade 2.3.4.4b H5N1 HPAIV infection in a cinereous vulture in South Korea and links severe clinicopathologic disease with a reassortant viral genome. The affected cinereous vulture developed marked neurologic dysfunction and showed nonsuppurative encephalitis, necrotizing myocarditis, and viral antigen distribution in the brain and heart, with the highest viral RNA burden detected in the brain.

Together, these findings are consistent with neurotropic and cardiotropic infections in this case. Genomic analyses showed that 26-JBN47 retained an East Asian H5N1 backbone in the HA, NA, and M segments, which clustered with G10-like viruses, whereas the internal genes reflected multiple reassortment histories involving regional AIV gene pools. The molecular marker profile was broadly consistent with contemporary avian-origin clade 2.3.4.4b H5N1 viruses and did not indicate advanced mammalian adaptation.

These findings show that cinereous vultures can develop severe fatal diseases after HPAIV infection and support their potential utility as sentinels of local or regional HPAIV circulation involving reassortant viruses near wildlife interfaces in East Asia.

(Continue . . . )
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https://afludiary.blogspot.com/2026/08/transb-emerg-dis-genomic-and.html

 

[Michael Coston]

J. Raptor Research: Rapid Decline of Nesting Peregrine Falcons in the San Francisco Bay Region of California Synchronous with an Outbreak of H5N1 HPAI​

#19,320

Twice last month (see here, and here) we looked at the enormous impact of HPAI H5 on raptors and other scavenger birds around the globe. Previously - over 2023-2024 - we followed attempts to protect endangered California Condors against the avian flu threat.

For those like me - born in the 1950s - this has an oddly familiar ring to it, as we witnessed a similar steep decline in raptors and songbirds due to the overuse of DDT and other chlorinated hydrocarbons, famously exposed by Rachel Carson in her 1962 book Silent Spring.

While demonized by many, that book eventually led to the banning of DDT in 1972, followed by the slow recovery of condors, eagles, and falcons. But it was a close thing, as by 1980 the California Condor was all but extinct.


Today we are witnessing the loss of tens, perhaps hundreds, of millions of wild birds due to HPAI. The USDA's list of (known) H5N1 wild bird infections lists more than 600 bald eagles, more than 500 hawks, more than 400 owls, and scores of falconsaffected by the virus, most of which were fatal.

These are just what has been reported in the U.S., and represent only a tiny fraction of the actual losses. While we lack good numbers, the impact of H5Nx on avian and mammalian wildlife around the globe has been staggering (see Nature Reviews: The Threat of Avian Influenza H5N1 Looms Over Global Biodiversity).

First a link to, and the abstract from, the study; followed by an excerpt from a press release. Follow the links to read both in their entirety. I'll have a bit more after the break.

Rapid Decline of Nesting Peregrine Falcons in the San Francisco Bay Region of California Synchronous with an Outbreak of H5N1 Highly Pathogenic Avian Influenza

Authors: Glucs, Zeka E., Hunt, W. Grainger, Kilpatrick, A. Marm, Ambrosini, Jan, Armstrong, Daniel J., et al.
Source: Journal of Raptor Research, 60(3) : 1-11 Published By: Raptor Research Foundation
URL: https://doi.org/10.3356/jrr26022
Abstract

After rebounding from near extirpation during the organochlorine era, breeding Peregrine Falcons (Falco peregrinus, hereafter peregrines) in California are again facing adversity, this time consistent with an outbreak of a highly pathogenic avian influenza (HPAI; Alphainfluenzavirus influenzae).

Following the first detection of the H5N1 variant clade 2.3.4.4b of HPAI in California wild birds in July 2022, we assembled data from long-term monitoring (2000–2025) of peregrine breeding territory occupancy in the broad vicinity of San Francisco Bay to examine possible impacts on falcon populations. Prior to the outbreak, 47 focal breeding territories had shown nearly complete occupancy by pairs (98.5% of 390 territory-years), with very few vacancies, single birds in attendance, or subadult pair members.

Within 8 mo of the outbreak, occupancy had dropped to 65.1%, and 2 yr later (2025), only 36.2% of territories remained occupied. Territories were increasingly occupied by single birds after the outbreak, but it is unclear whether these were survivors or floaters attempting to fill vacant territories where both pair members had perished. The high vacancy rates also signaled an impact upon floaters (nonbreeding adults) that normally buffer breeding territory occupancy in healthy peregrine populations. From October 2022 through November 2025, 17 peregrine fatalities were diagnosed with H5N1 within our study area.

Evidence that H5N1 caused these territory vacancies includes (1) the temporal coincidence of occupancy loss with the outbreak and (2) the lethality of the virus to peregrines and its confirmed presence in their prey in our study area. Our study reaffirms the value of long-term territory occupancy monitoring in this sentinel species.

(Continue . . . )

First DDT now the flu: Peregrine falcons in San Francisco Bay area hit hard by H5N1 variant

Raptor Research Foundation

Highly Pathogenic Avian Influenza (HPAI) featured prominently in the news during 2020 as it took the lives of millions of birds across the globe. While the worst seems to be behind us, population-level effects are just now emerging. A new study published in the Journal of Raptor Research, titled “Rapid Decline of Nesting Peregrine Falcons in the San Francisco Bay Region of California Synchronous with an Outbreak of H5N1 Highly Pathogenic Avian Influenza,” reports an alarming decrease in the number of occupied territories for a population of Peregrine Falcons (Falco peregrinus) that has maintained a longstanding presence in coastal California. As top predators, peregrines show warning signs when the health of their food web is jeopardized. They indicated the threat of DDT to wildlife in the 1960’s, and they are once again sounding the alarm to those who know where to look.

Highly Pathogenic Avian Influenza (HPAI) is an infectious disease that typically remains at low levels in wild bird populations. However, in 2020, the variant H5N1 emerged and ran amuck in what is now considered one of the most severe disease outbreaks to affect large animal populations ever recorded. Infections were documented in 400 bird species and at least 50 mammal species that year. Waterbirds are particularly susceptible to becoming carriers of HPAI, so predators and scavengers that feed on them are at a higher risk of exposure. Peregrines are master bird hunters and therefore primed to encounter this bird-born illness. However, it can be challenging to verify cause-of-death for raptors because of their low densities and the challenge of finding their carcasses, so raptor biologists must employ other tools to investigate population-level responses.

Lead author on the study Zeka Glucs, Director or the Predatory Bird Research Group at the University of California Santa Cruz, worked with a team of researchers to compare the presence of Peregrine Falcons on known territories in the Bay Area before and after the H5N1 outbreak, which was first detected in the state in 2022. They accessed a long-term dataset from 2000-2025 to examine trends in peregrine presence, underscoring the importance of maintaining research that spans decades.

The team found that prior to the H5N1 outbreak, 47 peregrine territories in the Bay Area were consistently occupied with stable breeding pairs. Following the outbreak, peregrine presence on these same territories dropped by 65% in three years, and the decline continues.

(Continue . . . )


Three years ago, in Avian Flu's New Normal: When the Extraordinary Becomes Ordinary, I wrote about the numbing effect that comes with the constant barrage of disturbing HPAI H5 reports from around the world.

Events that were nearly unthinkable five years ago (e.g. Repeated trans-Atlantic introduction of avian flu from Europe, the spread of HPAI H5 across the length of South America, numerous spillovers of H5 into mammalian species, the arrival of HPAI H5 to Antarctica, and most recently to Australia ) have now become `the new normal'.

Even if HPAI H5 never sparks a pandemic in humans, it is already a panzootic affecting the entire globe. One that already manifests itself in higher food costs, increased food insecurity, and growing public health and surveillance costs.

How the loss of millions of wild birds and mammals will ultimately affect humanity is a matter of debate, but it is hard to envision a good outcome.

Meanwhile, H5N1 marches on.


https://afludiary.blogspot.com/2026/09/j-raptor-research-rapid-decline-of.html