Legionellosis in Poland in 2022-2024

Objective The aim is to assess the epidemiological situation of legionellosis in Poland in 2022-2024 compared with previous years. Material and methods The assessment used data from mandatory national epidemiological surveillance published in the “Infectious Diseases and Poisonings in Poland” bulletins for 2013-2024 and individual legionellosis case reports recorded in the national infectious disease registry (EpiBase) in 2022-2024. Results In 2022-2024, 1,031 cases of legionellosis were registered in Poland, including 987 cases of Legionnaires’ disease and 44 cases of Pontiac fever. Notifications increased almost fourfold in 2023 compared with 2022 and remained high in 2024. Mean annual incidence in 2022-2024 was 0.91 per 100,000 population, over five times higher than in 2018-2021. Mean annual incidence increased in all voivodeships, with the highest value in 2022-2024 recorded in Podkarpackie Voivodeship, substantially influenced by the 2023 outbreak in Rzeszów and the surrounding area (166 cases). Legionnaires’ disease more frequently affected men, and incidence increased with age. The highest incidence was recorded among men aged 65 years and older. Most cases were sporadic (82.2%). Hospitalisation was required in 98.8% of patients, and deaths were recorded in 12.2% according to State Sanitary Inspection data. Most infections were acquired in Poland, with local exposure predominating among domestic cases. Conclusions The increase in legionellosis notifications in 2022-2024 was not attributable solely to the large outbreak in Rzeszów and the surrounding area. It may partly reflect improved case detection and reporting, although this effect cannot be distinguished from a true increase in cases. Incidence in Poland remains below the EU/EEA average. Maintaining diagnostic vigilance and the capacity to rapidly detect case clusters and investigate potential common sources of exposure remains important.