Several pathogens are known to affect the respiratory tract of pigs resulting in decreased health and welfare. Porcine parainfluenza virus 1 (PPIV1) and swine orthopneumovirus (SOV) have been identified as novel viruses in pigs. The pathogenicity of PPIV1 has been investigated experimentally by one research group, whereas SOV is yet to be studied. In this experimental trial, two groups of eight pigs were inoculated with a European isolate of PPIV1 or a pool of SOV RNA-positive clinical nasal swab material, and one group of four pigs with culture medium only (negative controls). Nasal swab samples were regularly collected to investigate viral RNA shedding, tissue samples for viral RNA and histopathological examinations, and blood samples to investigate seroconversion. All SOV inoculated pigs tested negative for SOV at 4 days post inoculation (DPI) and therefore, four of these pigs were transferred to the group with the PPIV1-infected pigs to assess direct-contact transmission. At DPI 4, two control and four pigs from each of the PPIV1 and SOV groups were euthanized and necropsied. The remaining pigs were euthanized at 14 DPI. No clinical signs, except for nasal discharge, were observed in any of the pigs. PPIV1 RNA shedding was observed from DPI 2-11 with peaks between DPI 4 and 7, and PPIV1 was transmitted horizontally to all direct-contact pigs. The highest viral RNA load was detected in the upper respiratory tract, i.e., nose, upper and lower trachea compared to the lower respiratory tract, i.e., bronchioles, and alveoli. Generally, a chronic tracheitis at 4 DPI, developing into chronic, erosive tracheitis at 14 DPI was observed in the PPIV1 groups and was supported by in situ detection of PPIV1 by RNAscope. Three pigs also developed mild, bronchointerstitial pneumonia at 14 DPI. All PPIV pigs euthanized at 14 DPI seroconverted. In conclusion, these results showed that PPIV1 is a primary porcine respiratory pathogen that causes breakage of the tracheal epithelial barrier and therefore can predispose to secondary infections. SOV's role as a porcine respiratory pathogen remains unknown, since no successful infection was established and it was not isolated in cells either.

Since 2020, high pathogenicity avian influenza H5Nx viruses of clade 2.3.4.4b have become enzootic in Europe, causing recurrent epidemic waves characterized by extensive reassortment events. Here, we describe the emergence of a single high-fitness genotype (EA-2024-DI) that has driven two consecutive waves, evolving into distinct sub-lineages. While its circulation is ongoing, during the 2025-2026 wave it caused an unprecedented number of cases in wild birds. Using phylodynamic analyses of a large dataset of genomic sequences, we compared the spatial diffusion and host transmission pattern of the EA-2024-DI sub-lineages across the three most recent epidemic waves (2023-2024, 2024-2025 and 2025-2026). We show that the genotype has persisted over time and has spread primarily through wild Anseriformes, but with a marked change in the transmission patterns between the different waves and a shift in the epicenter from Eastern to Central Europe, the latter having emerged as an important hub for virus diffusion throughout Europe. Our results reveal a recent increase in the frequency of viruses from wild and domestic mammals carrying mutations enhancing virus replication in mammalian hosts, highlighting the importance of proactive monitoring of this group of hosts to better understand its role in the virus ecology and evolution.

In February 2026, a highly pathogenic avian influenza (HPAI) A(H5N1) outbreak in a poultry holding in Sigmaringen, Germany, affected poultry and domestic cats, with infection confirmed by RT-qPCR. A One Health investigation identified 17 exposed humans, one of whom developed respiratory symptoms but tested negative for HPAI A(H5N1) (human coronavirus OC43 detected). Serological testing used haemagglutination inhibition assays. This outbreak highlights zoonotic risk, mammalian spillover and the need for coordinated veterinary and public health response and preventive measures.

In autumn 2025, highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus, genotype EA-2024-DI.2.1, caused systemic infections leading to a mass mortality event among the western migrating subpopulation of Eurasian cranes (Grus grus) in Germany. Gregarious behavior at feeding and resting sites likely promoted rapid viral spread within the population.

Zoos with avian populations are vulnerable to incursions of the high pathogenicity avian influenza virus (HPAIV) H5Nx due to the free-range husbandry, bird population density and shared open water areas between zoo birds and wild waterfowl. An outbreak of HPAIV H5N1, clade 2.3.4.4b, genotype EA AB, at the Zoological Garden Karlsruhe, Germany, in 2022, was managed applying legal restriction measures but exceptionally exempting culling orders for RT-qPCR-positive but clinically healthy birds. A critical factor in the zoo’s response was the implementation of a segregation concept approved in advance. The entire bird population could be rapidly separated into epidemiological housing units (epUs) cared for by separate staff. A total of 79 birds initially tested RT-qPCR-positive, but only 21 (26.6%) clinically diseased birds had to be euthanized or succumbed. Seroconversion amounted to 94.8% of the remaining 58 birds. Extensive RT-qPCR investigations of 3,634 samples confirmed infections remained confined to three initially infected epUs out of a total of 25. Spread of virus in the infected epUs was limited to 3 weeks after segregation. In the cohort of infected pelicans, surviving individuals remained seropositive with elevated levels of H5-specific antibody titers for the following 2 years suggesting ongoing protection. The described science-based control measures rested on a legally binding yet interpretive statement regarding the pertinent animal health legislation are exemplary for managing an outbreak of high pathogenicity avian influenza (HPAI) in zoos.

Abstract Vaccination against high pathogenicity avian influenza virus (HPAIV) is increasingly used to protect poultry, but vaccine performance is commonly inferred from clinical protection and virus shedding rather than measured transmission. We asked whether reproduction numbers from controlled transmission experiments can quantify how vaccination changes infection dynamics in virus-exposed geese, i.e. susceptibility and infectiousness. Domestic geese were prime-boost vaccinated with an H5 clade 2.3.4.4b RNA-amplicon vaccine and challenged with homologous HPAIV H5N1. Replicats of seeder-sentinel groups represented transmission among unvaccinated animals, to vaccinated contacts, and from vaccinated breakthrough-infected animals. Vaccinated directly challenged geese remained clinically protected although all became productively infected. Estimated reproduction numbers were R 0 =4.7 (95% CI, 2.8-8.0) among unvaccinated geese, R s =2.6 (1.6-4.5) for transmission to vaccinated contacts, R i =3.7 (2.0-6.8) for transmission from vaccinated infected geese, and R vacc =2.0 (0.8-4.9) for a fully vaccinated population. Vaccination reduced transmission but, under these experimental exposure conditions, did not reduce the point estimate for R vacc below one. Even though vaccinated infected geese shed substantially less viral RNA, infectiousness was sufficient to sustain transmission in vaccinated geese, indicating that RNA shedding alone may not reliably predict efficacy of transmission reduction. Experimental reproduction numbers therefore provide a direct population-level complement to conventional vaccine testing protocols and can separate effects on susceptibility from effects on onward transmission. Author Summary Vaccines against high pathogenicity avian influenza are usually evaluated by asking whether they prevent disease and reduce the amount of virus shed by infected birds. For disease control, however, it is equally important to know whether vaccination prevents onward transmission. We used domestic geese infected with H5N1 avian influenza virus to test whether this effect can be measured directly in small transmission experiments. By co-housing vaccinated and unvaccinated infected birds with vaccinated or unvaccinated contact birds, we estimated reproduction numbers for different transmission circumstances. Vaccination fully protected geese from clinical disease and reduced viral RNA shedding, but it did not prevent infection or transmission. The estimated reproduction number fell from 4.7 among unvaccinated geese to 2.0 for transmission to a fully vaccinated population, although the confidence interval was wide. Notably, the reduction in viral RNA shedding overestimated the effect on infectiousness. Thus, shedding alone may overstate how strongly a vaccine limits transmission. Directly estimating transmission can therefore add important information to conventional vaccine- efficacy studies and may improve comparisons between vaccines.

Abstract Background Swine influenza A virus (swIAV) is a major contributor to respiratory disease in pigs and represents a One-Health concern. This study evaluated whether slaughterhouse sampling can complement or partially substitute on-farm monitoring by comparing slaughterhouse-derived sample specimens for swIAV detection and subtype characterization. Results Twenty-one pig farms in Germany were enrolled, and one batch of fatteners per farm was monitored longitudinally using pen-based oral fluids (OFs) at three predefined time points during fattening. In case of acute respiratory distress, tracheobronchial swabs (TBS) were collected from 15 affected pigs. At slaughter, 30 pigs per farm were sampled and tested for swIAV by qPCR, yielding OFs, nasal swabs before and after scalding (NS I/NS II), bronchial swabs (BS), lung tissue (LT), and serum. Overall, 18/21 farms (85.7%) were classified as swIAV-positive, with a seroprevalence of 92.4% in the study population. During fattening, swIAV-RNA was detected in OFs collected on-farm in 7/21 farms (33.3%) at least once, most frequently at the beginning of fattening. Among 15 farms with TBS sampling, swIAV-RNA was detected in 4 farms (26.7%). At slaughter, swIAV-RNA was detected in at least one matrix on 7/21 farms and in 74/540 pigs (13.7%). Detection probability at slaughter differed by specimen: lower respiratory tract samples showed higher detection rates and lower Ct-values than NS (BS: 9.7%, LT: 10.9%; NS: 6.3%). Diagnostic agreement between materials ranged from fair to moderate, highest between BS and LT (κ = 0.58; p < 0.001). Slaughterhouse OFs showed low sensitivity. From selected RT-qPCR-positive samples with Ct < 33, BS yielded the highest proportion of successfully subtyped samples. Subtypes HA-1 C.2.1 (H1avN1EA), HA-1 C.2.4 (H1avN2G), and HA-1B.1 (H1huN2G) were identified in 4/7 RT-qPCR-positive farms. Conclusion Despite longitudinal OF sampling during fattening and additional TBS collection during acute respiratory disease, swIAV-RNA was only detected in a subset of seropositive farms. Molecular detection at slaughter was likewise restricted, whereas serology substantially improved herd-level identification. Among PCR-based sample types in slaughter pigs, BS demonstrated the highest diagnostic yield and suitability for subtype characterization. Even combined, on-farm and slaughterhouse RT-qPCR approaches remained constrained by the transient nature of swIAV shedding. Slaughterhouse sampling therefore complements—but does not replace—structured on-farm investigations for comprehensive surveillance.

The highly pathogenic avian influenza viruses of subtype H5N1 represent a major threat to animal and public health. The current panzootic with H5 clade 2.3.4.4b has caused numerous, widespread outbreaks in various domestic and wild avian species with high mortalities, massive losses, and a high frequency of spillover events to unexpected novel mammalian hosts, such as dairy cows. The global H5N1 situation raises serious concerns about zoonotic risks due to effective mammal-to-mammal transmission. Therefore, it is critical to increase surveillance intensity of a broadened species range, particularly at the human-animal interface. For this purpose, reliable and cost-effective serological tools that are easy to perform and suitable for high-throughput screening are critically needed. The newly developed double-antigen enzyme-linked immunosorbent assay format employing a luminescence-based detection technology has demonstrated compliance with such prerequisites. The assay allowed sensitive and specific detection of antibodies directed against H5 hemagglutinin of clade 2.3.4.4b in a wide range of birds and mammals, including humans. Furthermore, it allowed differentiating H5 anti-head-specific from cross-reacting anti-stalk antibodies, which represents a valuable feature with regard to the monitoring of future vaccination programs with H5-specific vaccines. Thus, the assay is a significant contribution to existing serological diagnostic tests for a clade-optimized and species-independent detection of influenza A virus antibodies. IMPORTANCE:The ongoing highly pathogenic avian influenza virus H5N1 panzootic has caused numerous outbreaks in domestic and wild animals, with frequent spillover events to unexpected host species, which underscores the importance of intensified surveillance. However, sensitive and specific multi-species serological assays represent a major gap. For this purpose, we developed a novel double-antigen enzyme-linked immunosorbent assay that employs an innovative luminescence-based readout strategy. The test allowed a highly sensitive and specific detection of H5-specific antibodies in a wide range of avian and mammalian species, including humans. It therefore represents a valuable contribution to improving species-independent serological diagnostic tools for the detection of influenza A virus antibodies.

Abstract Adjuvants function as an enhancer and activator of the immune response and can be of pivotal importance for the efficacy of vaccines. AS01, which is a liposome formulation spiked with the saponin derivate QS-21 and the detoxified lipopolysaccharide MPL-A, and AS03, which is a squalene-based oil in water emulsion that contains antioxidant tocopherol, are modern, highly potent adjuvants that became integral to innovative vaccines. In the current study, guinea pigs –a well-established small animal model for human influenza-infections– were subcutaneously vaccinated with an influenza H5N1-antigen formulated with AS01, AS03, aluminium hydroxide or left unformulated. The induction of T- and B cells specific for the influenza antigen was assessed in dependence of the antigen formulation. H5N1-specific T cell responses were observed with all adjuvant formulations, but after six months were highest in the AS01- and AS03-immunized groups. The influenza specific antibody titres were highest in AS03-vaccinated guinea pigs. Importantly, AS03- and AS01-formulated influenza antigen also induced crossreactive antibodies inhibiting related H5N3- but not a distant H5N8-influenza strain. At the same time, it was observed that animals, which received the egg-produced H5N1 split antigen in combination with AS03, mounted xenoreactive, opsonizing antibodies that bound to chicken fibroblasts. No reactivity was observed to human fibroblasts. In summary, our results confirm the superior adjuvanticity of AS03 and of AS01 as compared to conventional alum or non-adjuvanted formulations. The presence of xenoreactive antibodies after AS03 vaccination was an unexpected observation. Further investigations will be required to appreciate the significance and identify the mechanisms of this findings.

Abstract Facing the emergence of highly pathogenic avian influenza virus (HPAIV) H5N1 clade 2.3.4.4b in birds and its circulation in dairy cattle, rapid and reliable assays to detect HPAIV infection in humans are needed in diagnostic laboratories worldwide. We adapted and evaluated the performance of a molecular influenza A subtyping assay for the detection of A(H1N1)pdm09, A(H3N2), A(H5) and a pan-influenza A target on a high-throughput, fully automated platform. Previously published target primers and probes (Panning et al., Terrier et al., and the World Health Organization) were modified for target inclusivity/exclusivity, and adapted to compatibility with the Roche cobas5800/6800/8800 system as multiplex reaction. To evaluate the analytical performance of the new subtyping assay external quality assessment (EQA) samples were used as standards and quantified by digital-PCR. Limits of detection determined by 95% probit analysis were 754.0 digital copies (dcp)/ml for A(H1N1)pdm09, 148.0 dcp/ml for A(H3N2), 156 dcp/ml for A(H5) and 45.2 dcp/ml for the influenza A pan-target. Linearity was assessed for each subtyping target over at least four log-steps (r2: 0.9969–0.9998). The assay showed 100% agreement with EQA samples, eluates from the Friedrich Loeffler Institut (Germany) tested positive for different influenza A subtypes, and CE-IVD manual tests using 132 clinical samples. No false positives were detected in the exclusivity set. Our new subtyping assay is fully automated, easily scalable and can be used in surveillance and routine clinical settings enabling the detection of HPAIV infections in humans and may contribute to limit potential transmission chains at an early stage. Words: 250/250.

RESEARCH HIGHLIGHTS:Multiple independent HPAIV H5N1 euBB incursions occurred in Germany in 2023.HPAIV H5N1 euBB caused mass mortality in black-headed gulls and common terns.Outbreaks reduced gull and tern breeding populations by 16% and 6%, respectively.Rising H5-seroprevalence in terns may have contributed to the fade-out of genotype euBB.

Background: The southern Baltic Sea coast is an important stopover region for wild waterbirds, particularly between late August and April. These birds can contribute to the maintenance and spread of viral and bacterial pathogens, including highly pathogenic avian influenza viruses (HPAIV) and antimicrobial-resistant bacteria such as ESBL-producing Escherichia (E.) coli. The continued circulation of HPAI H5 viruses of the gs/Gd lineage has caused unprecedented global outbreaks in poultry and wild birds. While passive surveillance of sick and dead birds remains the main approach for HPAIV detection, complementary active surveillance of apparently healthy birds using simple, non-invasive sampling is needed to better understand virus ecology and evolution. Methods: From June 2022 to December 2023, we deployed shallow plastic bins with coastal brackish water and wheat grains along the Greifswalder Bodden shore, Baltic Sea, Germany, to attract wild waterbirds. After bird visits, water samples were analyzed for influenza A virus by RT-qPCR. In July 2022, four samples were cultured for ESBL-producing E. coli. Results: Camera monitoring confirmed that mallards (Anas platyrhynchos) were the main visitors, feeding and interacting intensively with the water. 222 water samples were analyzed for viral RNA; 13 (5.9%) were avian influenza virus-positive, including HPAI H5 (clade 2.3.4.4b) and low-pathogenic subtypes H3N8 and H11N9. All four samples yielded ESBL-producing E. coli, including one isolate of sequence type ST58. Conclusion: This non-invasive approach is a promising tool for environmental surveillance of viral and bacterial pathogens, with sensitivity expected to improve through enrichment techniques targeting pathogens in water.

Highly pathogenic avian influenza of subtype H5N1 (HPAIV H5N1) reached Antarctica in late 2023/2024 breeding season, but the host ecology and movement processes shaping its incursion and spread remain poorly resolved. We investigated these mechanisms by integrating viral genomics, multi-season serology, and seabird movement data at King George Island (Fildes Peninsula, South Shetland Islands), a likely gateway between South America and the Antarctic Peninsula. Across three breeding seasons (2022/23–2024/25), we collected swabs and blood serum from key scavenging and predatory seabirds (Brown skua, South Polar skua, Southern Giant petrel) and paired these data with light-level geolocator tracks (10–16 full annual tracks per species) and breeding-season GPS tracks (10–20 individuals per species). Phylogenetic analyses including three newly generated HPAIV H5N1 genomes from infected Brown skuas placed these viruses within the South Georgia–Antarctic lineage, consistent with introduction via South Georgia followed by onward spread within the region. Longitudinal serology revealed a rapid increase in cumulative exposure in scavenging species, with antibodies against influenza A virus’ nucleoprotein and hemagglutinin subtype H5 rising to high levels by 2024/25 in Brown skuas (52.2%) and Southern Giant petrels (62.5%), but remaining markedly lower in South Polar skuas (12.5%), consistent with their more pelagic and less scavenging foraging behaviour. Tracking showed that migratory connectivity was greatest during the non-breeding period but contracted rapidly during colony return and early breeding. In contrast, network simulations parameterized by high-percentile breeding-season foraging distances indicated strong peninsula-wide connectivity and non-zero potential links toward South Georgia and other sub-Antarctic stepping-stones. Together, these results provide a mechanistic, host-based framework suggesting that HPAIV H5N1 likely reached Antarctica through the South Georgia pathway, but that its regional spread was shaped primarily by foraging ecology and breeding-season movement networks rather than by long-distance migration.

Scavenging domestic ducks significantly contribute to the transmission and maintenance of highly pathogenic H5N1 clade 2.3.4.4b avian influenza viruses in Bangladesh, a strain of growing global concern due to its broad host range, high pathogenicity, and spillover potential. This study investigates the molecular epidemiology and pathology of HPAI H5N1 viruses in unvaccinated scavenging ducks in Bangladesh, with the goal of assessing viral evolution and associated disease outcomes. Between June 2022 and March 2024, 40 scavenging duck flocks were investigated for HPAI outbreaks. Active HPAIV H5N1 infection was detected in 35% (14/40) of the flocks using RT-qPCR. Affected ducks exhibited clinical signs of incoordination, torticollis, and paralysis. Pathological examination revealed prominent meningoencephalitis, encephalopathy and encephalomalacia, along with widespread lesions in the trachea, lungs, liver, and spleen, indicative of systemic HPAIV infection. A phylogenetic analysis of full-genome sequences confirmed the continued circulation of clade 2.3.2.1a genotype G2 in these ducks. Notably, two samples of 2022 and 2023 harbored HPAIV H5N1 of clade 2.3.4.4b, showing genetic similarity to H5N1 strains circulating in Korea and Vietnam. A mutation analysis of the HA protein in clade 2.3.4.4b viruses revealed key substitutions, including T156A (loss of an N-linked glycosylation site), S141P (antigenic site A), and E193R/K (receptor-binding pocket), indicating potential antigenic drift and receptor-binding adaptation compared to clade 2.3.2.1a. The emergence of clade 2.3.4.4b with the first report of neurological and systemic lesions suggests ongoing viral evolution with increased pathogenic potential for ducks. These findings highlight the urgent need for enhanced surveillance and biosecurity to control HPAI spread in Bangladesh.

Background/Objectives: The risk of the introduction of highly pathogenic avian influenza virus (HPAIV) in geese breeding and fattening flocks is heightened due to the necessity of free-range access to grazing grounds. This study aimed to evaluate the safety, immunogenicity, and protective efficacy of five commercial vaccines against HPAIV subtype H5N1 (clade 2.3.4.4b) in subadult fattening geese. Methods: A prime-boost vaccination trial was conducted using five commercial vaccines, including H5 expressing vaccines of novel technology (subunit, vector, RNA) and whole inactivated virus (WIV) vaccines. Based on serological results, one RNA and one WIV vaccine were selected for a homologous challenge experiment. Results: Two vaccines of novel technology (vector, RNA) required a booster dose to raise specific antibodies titers above a threshold of four log2 using a hemagglutination inhibition (HI) assay, whereas a subunit vaccine and two WIV vaccines induced seroconversion after primary vaccination. In the challenge experiment, all unvaccinated control geese succumbed to infection by day four. In contrast, all vaccinated geese that had seroconverted exhibited full clinical protection. Although sterile immunity was not achieved, viral excretion was significantly reduced in the vaccinated groups compared to controls. Conclusions: Vaccination substantially mitigated the impact of HPAIV H5N1, clade 2.3.4.4b infection in geese, greatly improving animal welfare by preventing severe disease. Additionally, there was a significant reduction in viral burden. Further studies are necessary to verify the potential of these vaccines to reduce susceptibility to infection and virus excretion in order to achieve suppression of the between-flock reproduction number to < 1 in geese flocks at high risk of infection.

The International Alliance for Biological Standardization (IABS), in collaboration with the World Organization for Animal Health (WOAH) convened a hybrid meeting on 22-23 October 2024 at the WOAH Headquarters (HQ) in Paris, France to discuss the global state of vaccination and surveillance for high pathogenicity avian influenza (HPAI) in poultry. The primary objective of the meeting was to advance vaccination acceptance to both control virus spread and reduce disease. Vaccination is increasingly recognized as a tool to complement biosecurity, movement controls and stamping-out of infected flocks. However, concerns persist regarding the risk of undetected, sustained transmission (silent infection) in vaccinated flocks as a result of inadequate surveillance. This has contributed to both vaccination hesitancy and trade barriers. The meeting aimed to assess the current state of the art regarding HPAI surveillance programs in vaccinated populations and their effectiveness. Representatives of multiple stakeholders were invited to share their experiences and perspectives on the use of vaccination and accompanying surveillance to control the growing H5N1 panzootic and its global impact. Several conclusions and recommendations emerged as essential to advancing the acceptance of vaccination strategies. These included (1) the utility of quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) as a sensitive, specific and economical tool to detect virus in vaccinated populations, (2) regular testing of dead birds within a flock as a highly effective method for early detection of outbreaks in vaccinated flocks and demonstrating freedom from infection and, (3) the importance of collecting information on circulating field strains in the selection of candidate vaccine antigens to ensure adequate efficacy. Testing sentinel birds was deemed less effective for surveillance and serological testing of vaccinated birds was considered more useful for assessing immunity levels than for determining the infection status of a flock. There was broad agreement on the need to standardize surveillance outcomes in terms of accepted confidence levels to promote safe and fair trade. However, it was acknowledged that context and pragmatic considerations will shape the development of situation specific plans, which must be statistically valid, scientifically sound, economically feasible and operationally sustainable for both governments and industry. Concomitantly, it was recommended that trade policies tied to vaccination and surveillance should be based solely on science and risks. To this end, enforcement of existing international rules and resolution of disputes are considered a shared responsibility. Peer reviewed publications were proposed as a central mechanism for developing the stronger guidelines needed to facilitate fair trade agreements and enable implementation of global vaccination programs. Rapid dissemination of information, consistent messaging and exchange of virus isolates were also seen as critical for coordinating an effective global response to controlling HPAI.

In autumn 2025, an unprecedented mass mortality event was observed among the western migrating subpopulation of Eurasian cranes ( Grus grus ) in Germany. Systemic infection with highly pathogenic avian influenza virus H5N1, clade 2.3.4.4b, genotype DI.2.1, was identified as the cause of acute death. The gregarious behavior of cranes at feeding and resting sites likely has contributed to the rapid and massive dissemination of viruses within the crane population. ### Competing Interest Statement The authors have declared no competing interest. European Union, 101084171

Highly pathogenic avian influenza viruses (HPAIV) of the H5 goose/Guangdong (gs/GD) lineage have repeatedly emerged in Germany since 2006. Rooted in the respective gs/GD lineages, HPAIV in Germany have genetically diversified into a plethora of clades and subclades and evolved into an assortment of sub- and genotypes. This technical note summarizes the genotype differentiation procedure, lists the successfully assigned genotypes and supplies corresponding reference sequences.