Tularemia is caused by Francisella tularensis, a small, fastidious, Gram-negative coccobacillus that is one of the most infectious pathogenic bacteria known. In Türkiye, the disease follows a distinctive epidemiological pattern: unlike the tick- and rabbit-associated transmission common in North America, water-associated spread dominates, and the oropharyngeal form of the illness is by far the most frequent presentation. The bacterium enters through the mucous membranes of the throat, typically when people drink untreated water contaminated by infected rodents or other small mammals, and then settles in the cervical lymph nodes, producing painful, often suppurating swellings in the neck.

The new study focused on patients diagnosed between January and May 2025 at two centers in Manisa province. To be included, patients had to show clinically compatible illness and a single positive microagglutination test, or MAT, titer of at least 1:160, the serological threshold conventionally accepted as supportive of tularemia diagnosis. The researchers retrospectively compiled demographic, epidemiological, clinical, laboratory, radiological, cytopathological, treatment, and outcome data for each case, and after the cluster was recognized, an environmental investigation was launched under the coordination of the Provincial Directorate of Health.

The demographic picture was striking. The median age of the thirteen patients was 33 years, with a range spanning 21 to 73, and eight of the thirteen, or 61.5 percent, were women. Twelve of the patients, 92.3 percent of the cohort, lived in rural Alaşehir and reported drinking natural spring water from the same local area, a shared exposure that immediately drew investigators’ attention. The thirteenth patient resided in Demirci, a different district, and had a separate exposure history with no epidemiological link to the Alaşehir spring-water consumption, effectively standing outside the cluster while still contributing to the clinical dataset.

Clinically, the oropharyngeal form dominated, accounting for ten of the thirteen cases, or 76.9 percent, while the remaining three patients, 23.1 percent, presented with the glandular form, in which lymph nodes enlarge without prominent throat involvement. Cervical lymphadenopathy was a universal finding, present in every patient in the cohort. Imaging played a central role in characterizing the disease: ultrasonography, computed tomography, and magnetic resonance imaging frequently demonstrated necrosis, liquefaction, abscess formation, or surrounding soft-tissue involvement within the affected nodes. These imaging features, while not specific to tularemia, are characteristic of the suppurative lymphadenitis the disease produces and helped clinicians gauge the extent of tissue destruction before deciding on surgical intervention.

One of the most instructive aspects of the report concerns what happened before the patients reached specialist care. Most had already received antimicrobial therapy, typically beta-lactam antibiotics such as amoxicillin or similar agents commonly prescribed for pharyngitis, and these treatments had proven ineffective. The explanation lies in bacterial biology: Francisella tularensis is an intracellular pathogen that is inherently resistant to beta-lactams because it produces a beta-lactamase and, more fundamentally, because it hides within host cells where such drugs penetrate poorly. Effective agents instead include fluoroquinolones, aminoglycosides, and tetracyclines, drugs that reach intracellular compartments. The authors emphasize that persistent cervical lymphadenopathy and tonsillopharyngitis unresponsive to beta-lactam antibiotics, particularly in rural settings with natural spring-water exposure, should prompt clinicians to consider tularemia in the differential diagnosis.

Because the cohort consisted of tertiary-care referrals with persistent symptoms or complicated lymphadenopathy, treatment was individualized according to disease duration and clinical response rather than delivered as a uniform protocol. In selected patients, drainage of abscessed lymph nodes was required, a reflection of how far the suppurative process had advanced by the time of referral. Despite the severity of presentations and the delays in specific therapy, the outcome was uniformly favorable: all thirteen patients achieved clinical recovery. This good prognosis is consistent with the natural history of oropharyngeal tularemia, which, while debilitating and protracted, carries a far lower mortality than the pneumonic or typhoidal forms of the disease.

The environmental investigation provided the strongest clue to the outbreak’s origin. A stored sample of natural spring water obtained from a household in Alaşehir was reported culture-positive for F. tularensis by the National Reference Laboratory, a significant finding given how difficult the organism is to cultivate outside specialized laboratories. Recovery of the bacterium from a water source consumed by twelve of the thirteen patients, all of whom drew from the same local area, strongly supports a waterborne transmission route. The authors are careful, however, to delineate the limits of the evidence: molecular confirmation or typing that would genetically link the environmental isolate to the human cases was not available, and direct microbiological confirmation from the patients themselves was absent, with diagnoses resting on serology and clinical compatibility. These gaps prevent definitive attribution of the transmission chain, leaving the waterborne source as probable rather than proven.

The methodological constraints of the study deserve attention as well. As a retrospective, observational analysis of a selected referral cohort, it captures the more severe end of the disease spectrum; milder cases in the community that resolved spontaneously or responded to empirical treatment would never have appeared in the dataset. The reliance on a single positive MAT titer rather than paired serology showing a fourfold rise means that, in principle, cross-reacting infections such as brucellosis could not be entirely excluded, although the clinical picture and the culture-positive water sample together make tularemia the overwhelmingly likely diagnosis. The authors also note that a preliminary version of the work was presented as a poster at the 14th Türkiye EKMUD Scientific Congress in Antalya in May 2026, and that the research received no specific grant funding.

For public health, the Manisa cluster is a reminder that tularemia remains an active threat in rural Anatolia, where untreated spring water is a cherished and widely consumed resource. The findings argue for surveillance of natural water sources in endemic districts, prompt notification when clusters of unexplained cervical lymphadenitis emerge, and education of both physicians and the public about the hazards of drinking untreated water. For clinicians everywhere, the message is equally clear: a sore throat with neck swellings that ignores beta-lactams deserves a second look, and a travel or exposure history that includes rural spring water should raise the possibility of Francisella tularensis long before the lymph nodes begin to liquefy.

Subject of Research: A waterborne tularemia cluster and its clinical and environmental investigation in Manisa, Türkiye

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

Article References: Erdem Kıvrak, E., Özer, D., Hafalır, T. İ., Özdem, Ş., Türkan, N., Şenol Akar, Ş., & Çetin, Ç. B. (2026). A Tularemia cluster in Manisa, Türkiye: clinical characteristics and investigation of a probable waterborne source. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14521-x

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14521-x

Keywords: tularemia, Francisella tularensis, oropharyngeal tularemia, cervical lymphadenopathy, waterborne transmission, Türkiye, Manisa, spring water, microagglutination test, environmental investigation, zoonotic disease, antibiotic resistance