Triangulated epidynamic-spatio-temporal analysis of A/H5N1 spillover to cats in Poland in June/July 2023 – letter to Eurosurveillance

One Health topics such as transmission of zoonotic agents of domestic/wild birds and environmental residue problems, food and feed safety become increasingly important to modern society in the post pandemic times. We performed epigenetic-spatio-temporal analysis of A/H5N1 epizootic in cats in Poland in Spring-Summer 2023 based on: 1) 30 (positive) and 27 (negative) cases from WOAH reference lab, 2) 19 RNA sentences of viruses3) suspected 87 cases submitted by animal owners (participatory epidemiology), 4) daily time series of i) Google queries for Avian Influenza (AI), cat’s disease and cats’ deaths, as well as ii) mentions of cat/cats and AI in social and traditional media. Data triangulation suggests the most likely scenarios based on Google queries, news and social media analysis, reference lab results and participatory epidemiology reports: 1) The first A/H5N1 cases were probably in cats in late May near the south-eastern border (based on the evidence from the retrospective media analysis and participatory reports). 2) The highest disease burden was in Pomerania (particularly Gdansk) in mid-June. 3) The highest positivity ratio was in Western Poland, indicating outbreak clusters in late June/early July. 4) Positive cases formed clear chains, supporting the environmental source hypotheses (on the connection to bird migration paths and nearness of nesting sites of water birds). 5) There are at least 2 (eastern and western Poland) separate genetic clusters of viruses. We recommend performing active monitoring (PCR and serology) of water birds in Pomerania and selected sites in Western Poland (as maybe some low viral pressure of active virus is still present at the end of July 2023). Retrospective epigenetic investigation of the south-eastern border area should be done to prove Lublin cases as the origin of the outbreak. Even that hypothesis of poultry meat/eggs (being feed for cats) contamination, seems to be unlikely (i.e. our method indicated that suspected positive cases situated far from bird migratory paths were wrongly geocoded or the results came form not accredited lab), aviary disease surveillance system needs to be updated to handle new pandemic threats.