Monthly summary of sampled birds

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

August 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 The data in this report are based on previously unpublished samples collected from July 2025 to August 2025.

2. RESULT

2.1 DATA COLLECTION
Since the last monthly report (published on 1st of August 2025; https://doi.org/10.5281/zenodo.16675124), and as of 15th July 2025, test results have been submitted for 23 samples taken from 23 individuals representing five taxa from one node in Europe (Table 1). Of the 23 collected samples, all were combined swabs (choana + cloacal). Of all samples, two were positive for avian influenza virus, none were positive for highly pathogenic avian influenza (HPAI) virus (Figure 1; Table 2). Both samples were of the N3 subtype, however, the haemagglutinin (HA) subtype could not be determined.

The most sampled species were European herring gull (16 individuals), and great cormorant (4 individuals; Table 1).

TABLE 1 Most recently sampled individuals in the SENTINEL Wild Birds project. Total number of individuals sampled in the wild, as well as number of individuals tested positive for avian influenza virus. The table includes previously unpublished samples from July to August 2025.

TABLE 2 Most recently collected samples in the SENTINEL Wild Birds project. Total number of collected samples as well as number of samples positive for avian influenza virus. The table includes previously unpublished samples from July to August 2025.

FIGURE 1 Sample sites in the SENTINEL Wild Birds project. Sample sites for the 23 individuals sampled in Lithuania. The figure includes previously unpublished samples from July to August 2025.

A weekly compilation of all 14,787 samples (positive and negative; including previously published), collected at each node from August 2024 to August 2025, can be seen in Figure 2.

FIGURE 2 Weekly summary of collected samples in the SENTINEL Wild Birds project. In total, 14,787 samples (negative samples in blue; avian influenza virus-positive samples in orange) have been collected at seven nodes between August 2024 and August 2025, yielding 1,042 samples positive for avian influenza virus, including 24 samples positive for HPAI virus. The figures also include samples published in previous reports.

2.2 GENOMICS SUMMARY
Since the last report was published on 1st of August 2025 (https://doi.org/10.5281/zenodo.16675124), and as of 15th August 2025, no new sequences have been generated from samples positive for avian influenza virus. The latest and previous Nextstrain builds are available on the SENTINEL Wild Birds Group (https://nextstrain.org/groups/SentinelWildBirds).

3. CONCLUSION
During summer, sampling activity was very low, with collections carried out only in Lithuania. Despite the small sample size of just 23 individuals, two tested positive for avian influenza virus. Both positives were detected in juvenile great cormorants caught as by-catch in fishing nets. This finding confirms that avian influenza virus continues to circulate in wild birds during summer, particularly among young, immuno-naïve individuals.

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)