An Outbreak of Pulmonary Tularemia in Slovenia in Summer 2024

Background: Tularemia is a rarely identified disease in Slovenia. In summer 2024, we detected a tularemia outbreak in the Kranjsko-Sorško polje, located in North-Western part of Slovenia. Aim: To describe the epidemiological investigations and preventive measures to contain the outbreak. Methods: The patients with confirmed tularemia were interviewed. Serology and PCR was used for microbiological confirmation of tularemia and in some patients by isolation from blood or by RT-PCR. Results: The majority of confirmed tularemia cases in 2024 were infected in the geographically limited area in North-Western part of Slovenia (38/46). Tularemia was confirmed in two patients by isolation Francisella tularensis subsp. holarctica from blood or wound, in one by blood PCR, and in the others by serology. Most cases were associated with mowing or harvesting hay with intensive dusting. Twenty-eight (75.7%) out of 37 cases developed pulmonary tularemia. Sixteen cases were hospitalized. After confirming the outbreak, we alerted medical professionals in the region and the general public using the regional and national media and website of National Institute of Public Health. Conclusions: Endemic tularemia in Slovenia is associated with handling wild life and presents in ulceroglandular form. In the localized outbreak in year 2024 there was an extraordinary upsurge of pulmonary tularemia, with many of the cases initially investigated for lung cancer based on the radiology reports. Due to dry weather condition in summer 2024, excessive dusting associated with mowing the grass and handling hay resulted in inhalation of infective aerosols leading to the infection with F. tularensis.