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Epidemiology, microbiology, and pathogenesis of tularemia

Robert L Penn, MD
Section Editors
Stephen B Calderwood, MD
Morven S Edwards, MD
Deputy Editor
Allyson Bloom, MD


Tularemia is the zoonotic infection caused by Francisella tularensis, an aerobic and fastidious gram-negative bacterium. Human infection occurs following contact with infected animals or invertebrate vectors. Synonyms include Francis' disease, deer-fly fever, rabbit fever, water-rat trappers' disease, wild hare disease (yato-byo), and Ohara's disease [1].

The epidemiology, microbiology, and pathogenesis of infection due to F. tularensis will be reviewed here. The clinical manifestations, diagnosis, treatment, and prevention of tularemia are discussed separately. (See "Clinical manifestations, diagnosis, and treatment of tularemia".)


Distribution — The majority of infections in humans and animals are caused by F. tularensis subspecies tularensis (the more virulent species) and F. tularensis subspecies holarctica. Human disease is rarely associated with the subspecies novicida, Francisella philomiragia, and Francisella hispaniensis [1-3].

In North America, F. tularensis has been described in the United States, Canada, and Mexico. In the United States, the majority of cases traditionally occur in the south-central states (figure 1) [4]. Over time, however, the southern border of tularemia in the United States has shifted northward [5]. As an example, the number of reported cases in Colorado, Nebraska, South Dakota, and Wyoming dramatically increased in 2015, and 74 percent of cases occurred in Arkansas, Colorado, Kansas, Missouri, Nebraska, Oklahoma, South Dakota, and Wyoming (figure 2) [6]. This is consistent with the predicted effects of climate change on the geographic distribution of tularemia [7].

Other countries known to have endemic tularemia include most European countries, the former Soviet Union, Tunisia, Turkey, Israel, Iran, China, and Japan. Tularemia is relatively uncommon in African countries, Australia, England, and South American countries.

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Literature review current through: Nov 2017. | This topic last updated: Sep 17, 2017.
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