A Tularemia cluster in Manisa, Türkiye: clinical characteristics and investigation of a probable waterborne source

Abstract Background Tularemia is a re-emerging zoonotic disease caused by Francisella tularensis. In Türkiye, water-associated transmission is an important epidemiological pattern and oropharyngeal disease is common. This study aimed to describe the clinical characteristics of a tularemia cluster identified in Manisa, western Türkiye, and to evaluate the epidemiological and environmental findings supporting a probable waterborne source. Methods This retrospective, observational, two-center study included 13 adult patients with clinically compatible tularemia and a single positive microagglutination test (MAT) titer of ≥ 1:160 diagnosed between January and May 2025. Demographic, epidemiological, clinical, laboratory, radiological, cytopathological, treatment, and outcome data were retrospectively collected. Twelve patients from Alaşehir reported natural spring-water consumption within the same local area, whereas one patient resided in Demirci and had a separate exposure history. Following recognition of the cluster, an environmental investigation was conducted under the coordination of the Provincial Directorate of Health. Results Thirteen patients were included. The median age was 33 years (range, 21–73 years), and eight (61.5%) were female. Twelve patients (92.3%) resided in rural Alaşehir and reported natural spring-water consumption within the same local area; one patient resided in Demirci and was not epidemiologically linked to that exposure. The oropharyngeal form was the most common presentation (10/13, 76.9%), followed by the glandular form (3/13, 23.1%). Cervical lymphadenopathy was present in all patients, and imaging frequently demonstrated necrosis, liquefaction, abscess formation, or surrounding soft-tissue involvement. Before referral, most patients had received antimicrobial therapy that was ineffective against tularemia. Because this was a selected tertiary-care referral cohort with persistent symptoms and/or complicated lymphadenopathy, treatment was individualized according to disease duration and clinical response; drainage was required in selected patients. All patients achieved clinical recovery. A stored natural spring-water sample obtained from a household in Alaşehir was reported culture-positive for F. tularensis by the National Reference Laboratory. Molecular confirmation or typing linking the environmental finding to the human cases was not available. Conclusions This cluster highlights the importance of considering tularemia in patients with persistent cervical lymphadenopathy and tonsillopharyngitis unresponsive to beta-lactam antibiotics, particularly in rural settings with natural spring-water exposure. The shared exposure among the Alaşehir cases and the culture-positive environmental sample support a probable waterborne source; however, the absence of direct microbiological confirmation of the human cases and molecular linkage prevents definitive attribution of the transmission chain.