​Monthly summary of sampled birds

The website will be updated regularly as more data from the project becomes available. Please check back for the latest information

​View older summaries

The Nextstrain builds are available on the SENTINEL Wild Birds Group - https://nextstrain.org/groups/SentinelWildBirds

October 2025

​1. OVERVIEW
SENTINEL Wild Birds aims to enhance the understanding of highly pathogenic avian influenza (HPAI) virus dynamics in wild bird populations by conducting active surveillance at key locations in and near Europe. These locations are divided into the following surveillance nodes: Node 1 Gulf of Finland (Finland, Estonia), Node 2 Southern Baltic Sea (Sweden, Latvia, Lithuania, Poland), Node 4 Eastern Black Sea (Georgia), Node 6 Lake Constance (Germany, Austria, Switzerland), Node 7 Veneto Region (Italy), Node 8 Camargue (France), and Node 9 Gulf of Cadiz (Spain). This monthly summary provides an update on sampled wild birds as part of an early warning system to support wildlife management and disease prevention efforts. The data in this report are based on previously unpublished samples collected from June 2025 to October 2025.

2. RESULT

2.1 DATA COLLECTION
Since the last monthly report was published on 7th of October 2025 (https://doi.org/10.5281/zenodo.17287099), and as of 15th October 2025, test results have been submitted for 3,335 samples taken from 1,966 individuals representing 55 taxa from six nodes in Europe (Table 1). Of the 3,335 collected samples, 1,505 (45%) were cloacal swabs, 1,376 (41%) tracheal/oropharyngeal swabs, 365 (11%) fecal samples, 70 (2%) combined swabs (choana + cloacal), 15 (<1%) pooled organs, and 4 (<1%) feather samples. Of all samples, 386 (12%) were positive for avian influenza virus, with one sample (a Mallard from Latvia) positive for highly pathogenic avian influenza (HPAI) virus (Figure 1; Table 2). In addition to this HPAI virus-positive sample, virological analysis (by PCR) confirmed one H13N6 virus in a European Herring Gull from Lithuania, one H6N5 in a Mallard from Austria, as well as one H3N2, one H6N5, one H12N2, and two H5 viruses with undetermined NA subtypes, all in hunted Mallards from Latvia.

The most sampled species were Mallard (612 individuals), Eurasian Teal (429 individuals), Dunlin (167 individuals), Sandwich Tern (121 individuals), and Common Tern (97 individuals; Table 1). High bird-level prevalence in species with a sample size of at least 50 individuals was found in Eurasian Teal (19%), Mallard (13%), and Black-headed Gull (11%; Table 1).

​2.2 GENOMICS SUMMARY
Since the last report was published on 7th of October (https://doi.org/10.5281/zenodo.17287099), and as of 15th of October 2025, two new sequences have been generated from samples positive for H5 avian influenza virus. The two samples were collected from Mallards in Estonia (Node 1 Gulf of Finland) and Latvia (Node 2 Southern Baltic Sea) and were of the H5N2 and H5N1 subtypes, respectively. Genetic analysis of the haemagglutinin (HA) gene sequence of the H5N2 from Node 1 Gulf of Finland was found to belong to the H5 Eurasian avian non-goose Guangdong (EA-nonGsGd) low pathogenicity avian influenza (LPAI) clade, whilst the sequence from Node 2 Southern Baltic Sea belonged to the H5 clade 2.3.4.4b of highly pathogenic avian influenza (HPAI) (Figure 3A).

The sequence from Estonia was found to be similar to other H5 LPAI sequences from the SENTINEL Wild bird project from Sweden (Node 2 Southern Baltic Sea) and France (Node 8 Camargue Region), as well as other Eurasian LPAI sequences (Figure 3B).

The sequence from Latvia, was determined to be the DI.2 genotype, according to the IZSVe classification (https://github.com/izsvenezie-virology/genin2), and was found to be similar to another sequence from Latvia (a Whooper Swan), as well as sequences from Europe and surrounding countries, including the DI.2 sequence collected in Georgia (Node 4 Eastern Black Sea) in February 2025 (Figure 3C).

The Nextstrain builds are available on the SENTINEL Wild Birds Group (https://nextstrain.org/groups/SentinelWildBirds).

Apart from the H5 genome sequences, an additional H6N5 sequence was generated from a sample collected in Latvia (Node 2 Southern Baltic Sea).

FIGURE 3 Phylogenetic analyses of the HA sequences generated by Node 1 Gulf of Finland and Node 2 Southern Baltic Sea. Image of the H5 HA sequences generated by the SENTINEL Wild Birds project, with the 2.3.4.4b and EA-nonGsGd clades highlighted. B. Zoom image of the HA tree focusing on the H5 low pathogenicity avian influenza (LPAI) EA-nonGsGd sequences from Node 1 Gulf of Finland, Node 2 Southern Baltic Sea and Node 8 Camargue Region. C. Zoom image of the HA tree focusing on the H5 highly pathogenic avian influenza (HPAI) clade 2.3.4.4b sequences from Node 2 Southern Baltic Sea and Node 4 Eastern Black Sea.

3. CONCLUSION
With close to 2,000 individuals analysed from more than 50 species in 10 countries during the current period, the coverage of active surveillance of wild birds in and near Europe remains substantial. As expected during autumn, when a large immuno-naïve juvenile population is present, an increase in avian influenza virus (AIV) prevalence has been observed.

Positive samples were mainly found in dabbling ducks around the Baltic Sea, particularly in Mallards, as well as in Georgia, where Eurasian Teals dominated. In both regions, large numbers of ducks congregate at this time of year, making them key hotspots for active surveillance of avian influenza in wild birds. High bird-level prevalence was recorded in Eurasian Teal (19%), Mallard (13%), and Black-headed Gull (11%), all species with large sample sizes. Additionally, notably high prevalence was observed in some less frequently sampled species such as Common Pochard (4 of 9 individuals; 44%), Northern Shoveler (4 of 11; 36%), and Garganey (2 of 8; 25%).

Importantly, one sample from a hunted Mallard in Latvia tested positive for HPAI H5N1 virus. Genetic analysis showed that the virus belongs to clade 2.3.4.4b (genotype DI.2), similar to previous detections in Latvia and Georgia earlier this year. This highlights the need for continued vigilance and preparedness for potential outbreaks, particularly as autumn migration proceeds.

In addition to the HPAI case, virological analysis (by PCR) detected several other subtypes: one H13N6 in a European Herring Gull from Lithuania, one H3N2, one H6N5, one H12N2, and two H5Nx in Mallards from Latvia, as well as another H6N5 in a Mallard from Austria. These findings reflect the ongoing circulation and diversity of low pathogenic avian influenza (LPAI) viruses in the region.

Despite substantial sampling of waders (over 300 individuals), no AIV-positive samples were detected in this group. This may suggest that waders are not a priority target group for AIV surveillance under current resource constraints. However, it should be noted that most wader samples were collected in July–August, when overall prevalence is typically low. A similar observation applies to gulls and terns. With the exception of Black-headed Gulls, over 300 individuals were sampled with only three positives recorded.

The increase in positive detections around the Baltic Sea, especially in Latvia, combined with ongoing bird migration, underscores the importance of intensified monitoring at key stopover and wintering sites across Europe in the coming months.

ACKNOWLEDGMENT
This report is based on data collected and analysed by fieldworkers, laboratory personnel, and node coordinators from the following organizations and institutions:

Node 1: LABRIS, Riigi Laboriuuringute ja Riskihindamise Keskus (Estonia); Ruokavirasto, Finnish Food Authority (Finland); University of Turku (Finland)

Node 2: Swedish National Veterinary Institute (SVA) (Sweden); Linnaeus University (Sweden); Institute of Food Safety, Animal Health and Environment “BIOR” (Latvia); National Food and Veterinary Risk Assessment Institute (Lithuania); State Food and Veterinary Service (Lithuania); National Veterinary Research Institute (Poland)

Node 4: Centre of Wildlife Disease Ecology (CWDE), Ilia State University; State Laboratory of Agriculture of Georgia

Node 6: Austrian Agency for Health and Food Safety (AGES) (Austria); Verein für die Betreuung des Naturschutzgebietes Rheindelta (Naturschutzverein Rheindelta) (Austria); Friedrich-Loeffler-Institute (FLI) (Germany); Max-Planck-Institut für Verhaltensbiologie (MPI) (Germany); National Reference Centre for Poultry and Rabbit Diseases (NRGK) (Switzerland); Swiss Institute for Virology and Immunology (IVI) (Switzerland)

Node 7: Istituto Zooprofilattico Sperimentale delle Venezie; Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA)

Node 8: École Nationale Vétérinaire de Toulouse (ENVT); INRAE (Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement); La Tour du Valat; Conservatoire d’Espaces Naturels d’Occitanie (CEN Occitanie); Laboratoire Départemental du Gard; Office Français de la Biodiversité (OFB); Ministère de l’Agriculture et de la Souveraineté Alimentaire; Muséum national d’Histoire naturelle (MNHN); Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail (ANSES)

Node 9: Martina Ferraguti, Josué Martínez-de la Puente, and Jordi Figuerola at Estación Biológica de Doñana (EBD-CSIC); Ursula Höfle at Grupo de Sanidad y Biotecnología (SaBio), Instituto de Investigación en Recursos Cinegéticos (IREC-CSIC); Elisa Pérez-Ramírez and Jovita Fernández-Pinero at Centro de Investigación en Sanidad Animal (CISA-INIA-CSIC) (Spain)