​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

February 2025 - Download here
January 2025 - Download here
December 2024 - Download here
November 2024 - Download here

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

February 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 The data in this report are based on previously unpublished samples collected from November 2024 to February 2025, along with backlogged samples from Georgia dating back to August 2024.

2. RESULT

2.1 DATA COLLECTION
Since the last monthly report (published on 30th of January 2025; https://doi.org/10.5281/zenodo.14772852), and as of 15th February 2025, test results have been submitted for 4296 samples taken from 2518 individual wild birds representing 29 taxa across six nodes in Europe (Table 1). Of the 4296 collected samples, 1781 (41 %) were cloacal swabs, 1679 (39 %) tracheal/oropharyngeal swabs, 649 (15 %) faecal samples, 115 (3 %) feather samples, 52 (1 %) combined swabs (choana + cloacal), 19 (<1 %) pooled organs, and one (<1 %) blood sample. Of all samples, 513 (11.9 %) from seven different taxa were positive for avian influenza virus, of which none were positive for highly pathogenic avian influenza (HPAI) virus (Figure 1; Table 2).  

The overall bird-level prevalence of avian influenza virus in these recently submitted samples was 17.5 %. The highest bird-level prevalence was found in Sweden (30.3 %; Table 1), and among the most frequently sampled birds, Mallard had a prevalence of 27.6 % (409 of 1484 individuals), Eurasian Teal 5.9 % (20 of 341 individuals), sentinel domestic Mallard 3.9 % (5 of 128 individuals), Pochard 2.7 % (2 of 77 individuals), and Black-headed Gull and Marbled Duck 0 % (0 of 174 and 0 of 123 individuals, respectively) (Table 1).

​2.2 GENOMICS SUMMARY
Since the last report was published on 30th of January (https://doi.org/10.5281/zenodo.14772852), and as of 15th February 2025, a total of 19 new sequences have been generated from samples positive for H5 avian influenza viruses. All 19 samples were collected from Mallards in Sweden (Node 2 Southern Baltic Sea), of which H5N2 (N=6), H5N3 (N=11) and H5Nx (N=1) subtypes were detected. Genetic analysis of the haemagglutinin (HA) gene sequences from 18 of these samples found that they belonged to the Eurasian non-Goose Guangdong (EA-nonGsGd) low pathogenicity avian influenza (LPAI) clade. For the final sample, the HA sequence was not recovered, and the subtype was inferred from PCR testing, therefore the clade cannot be determined. The majority of the HA gene sequences from these samples, showed similarity to H5N2 and H5N3 LPAI viruses previously detected at Node 2 Southern Baltic Sea (see November 2024 report: https://zenodo.org/records/14507721), as well as sequences from across Europe and Asia (Figure 3, Group 1). However, one of the HA sequences did not cluster with the other sequences collected from this node and grouped with sequences from Europe only (Figure 3, Group 2). This could be suggestive of two distinct incursions of similar, yet distinct H5 LPAI viruses into the wild bird population being sampled within Node 2 Southern Baltic Sea.

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

In addition to the H5 genome sequences, a further 38 non-H5 genome sequences were generated from Node 2 Southern Baltic Sea. All of these samples were collected from Mallards in Sweden, and as seen in the previous report (see January 2025 report: https://zenodo.org/records/14772852), wide subtypic diversity was observed (5 x H1N2, 1 x H4N3, 1 x H4N4, 10 x H4N6, 1 x H4N9, 3 x H6N8, 1 x H10N3, 5 x H10N4, 1 x H11N6, 8 x H11N9 and 2 x HxN3).

3. CONCLUSION
The number of analysed samples has more than doubled since the last published report in January 2025, with the majority originating from Sweden and Georgia. With nearly all samples collected in 2024 now analysed, the peak prevalence (76.2%) was observed in week 37 (week from 9 September 2024). However, this peak is based on a relatively small sample size (42 samples, of which 32 tested positive for avian influenza virus). A second peak occurred in week 45 (week from 4 November 2024), with a prevalence of 29.2% (849 samples collected, of which 248 tested positive for avian influenza virus). These peaks are primarily based on samples collected from Mallards in Sweden. Positive detections of avian influenza virus in Mallards are common in Sweden, particularly at Ottenby, where the wild bird trap is located, during autumn migration. While the proportion of positive samples is relatively high, the number of HPAI cases has so far been low, with only 22 confirmed cases in 2024, all in Eurasian Teals in Italy.

Although there is a slight backlog of samples collected in 2025, the overall prevalence remains low at 1.4%, with no confirmed cases of HPAI virus.