Tularemia outbreak investigations: A review

Abstract

Background: Tularemia is a highly contagious, multi-systemic zoonotic disease caused by francisella tularensis that can give rise to outbreaks. Through reviewing published outbreak investigations, we wanted to put forth the characteristics of the outbreaks, affected people, epidemiological studies overall and their results for better understanding these outbreaks and to gather information under a single document. Methods and materials: Two searchers were conducted using: «tularemia outbreak» and «francisella tularensis outbreak» in title and/or abstract using PubMed database for articles that had been published until 01.10.2018. There were no limitation for starting date. Articles in English, Spanish and Turkish languages were considered. Results: In total 50 articles (22 studies after the first search and 28 after the second one) were finally included from both searches: most studies (68%) informing on human tularemia outbreaks were from Turkey, Spain and U.S.A. Twenty-nine articles mentioned water as the possible source of the outbreak, seven of them also mentioned food as the possible source. However, none of them reported detection of the agent in food samples. Four articles mentioned airborne infection as a probable route. Thirty-five of the studies were descriptive. Twenty-one of them comunicated delay and/or misdiagnose, prior to accurate diagnosis of tularemia infections. Treatment with inadequate medication such as beta-lactams, macrolides, penicillin and anti-tuberculosis therapy without recovery is noted in articles mentioning misdiagnosis. Conclusion: Tularemia outbreaks continue generating public health concerns, especially in the northern hemisphere. Occupation and direct or indirect contact with infected animals can be risk factors. Tularemia outbreaks can occur via several transmission ways; evidence shows that even though a certain group, for example one family, is infected with the same source, individuals can develop different forms of the disease according to the port of entry. Developed in a timely manner, epidemiological analysis and investigation supported with laboratory confirmations could provide deeper understanding on tularemia outbreaks and facilitate the process of making evidence-based outbreak interventions avoiding misdiagnosis and inappropriate use of antibiotics.