Meningitis and encephalitis in Poland in 2023.

Background: In Poland, meningitis and/or encephalitis, regardless of etiology, are subject to routine epidemiological surveillance. This paper presents an analysis of meningitis and/or encephalitis in 2023, caused by Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae and tick-borne encephalitis virus.

Objective: The aim of the study was to assess the epidemiological situation of meningitis and encephalitis in Poland in 2023 taking into account the impact of the COVID-19 pandemic.

Methods: To evaluate the epidemiological situation of neuroinfections in Poland, data sent to NIPH NIH-NRI by the Sanitary and Epidemiological Stations and published in the annual bulletin: "Infectious diseases and poisonings in Poland in 2023" and "Vaccinations in Poland in 2023" as well as individual epidemiological reports registered in the EpiBaza system.

Results: In 2023, there were 2754 cases of meningitis and/or encephalitis, an increase of 57.6% compared to 2022 (1748 cases) and 22.5% against 2019 (2249 cases). Incidences of bacterial etiology, including neuroborreliosis, increased by 39.7% (from 848 in 2022 to 1185 in 2023, incidence: 2.24 to 3.14 per 100,000). The incidence for N. meningitidis increased by 17.6(from 0.17 to 0.20), for H. influenzae by 125% (from 0.04 to 0.09), and for S. pneumoniae by 30.9% (from 0.55 to 0.72). Viral infections accounted for 57% of the total, and their number increased by 74.3% (from 900 in 2022 to 1,569 in 2023). The highest number of viral infections was for tick-borne encephalitis, with 661 cases (up 48.2%).

Conclusions: 2023 showed an overall upward trend in the number of registered cases of meningitis and/or encephalitis of bacterial and viral etiology compared to 2022. The number of cases was 22.5% higher than in 2019, the period before the COVID-19 pandemic. These results indicate significant changes in the epidemiological situation, which may be due to improved diagnosis, a change in epidemiological trends and a higher number of reported cases. The observed increase underscores the need for further monitoring and implementation of effective preventive measures to reduce future cases.