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. 2006 Jul;12(7):1113-8.
doi: 10.3201/eid1207.051504.

Epidemiologic and molecular analysis of human tularemia, United States, 1964-2004

J Erin Staples  1 , Kristy A Kubota, Linda G Chalcraft, Paul S Mead, Jeannine M Petersen
Affiliations

Epidemiologic and molecular analysis of human tularemia, United States, 1964-2004

J Erin Staples et al. Emerg Infect Dis. 2006 Jul.

Abstract

Tularemia in the United States is caused by 2 subspecies of Francisella tularensis, subspecies tularensis (type A) and subspecies holarctica (type B). We compared clinical and demographic features of human tularemia cases from 1964 to 2004 from 39 states in which an isolate was recovered and subtyped. Our data indicate that type A and type B infections differ with respect to affected populations, anatomic site of isolation, and geographic distribution. Molecular subtyping with pulsed-field gel electrophoresis further defined 2 subpopulations of type A (type A-east and type A-west) that differ with respect to geographic distribution, disease outcome, and transmission. Our data suggest that type A-west infections are less severe than either type B or type A-east infections. Through a combined epidemiologic and molecular approach to human cases of tularemia, we provide new insights into the disease for future investigation.

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Figures

Figure 1
Figure 1
Geographic distribution for type A (red circles) and type B (yellow circles) Francisella tularensis isolates from humans, contiguous United States, 1964–2004. Each circle represents 1 isolate. Isolates were plotted randomly within the county of exposure. The 100th meridian is indicated by the black line transecting the United States. County of exposure was known for 198 (63%) isolates.
Figure 2
Figure 2
PmeI pulsed-field gel electrophoresis patterns for Francisella tularensis type A and type B. Lanes 1 and 8, Salmonella enterica serotype Braenderup standard; lane 2, Virginia 1997 type B; lane 3, Indiana 1999 type B; lane 4, New York 2004 type A-east; lane 5, Oklahoma 2001 type A-east; lane 6, Oregon 2004 type A-west; lane 7, California 2002 type A-west.
Figure 3
Figure 3
Dendrogram based on PmeI pulsed-field gel electrophoresis patterns of 41 Francisella tularensis type A and 22 type B isolates from humans. A 1.5% optimization and 1.5% tolerance were used to calculate Dice similarity coefficients. Isolate information is given with respect to exposure state and year.
Figure 4
Figure 4
Seasonal distribution of type A and type B Francisella tularensis isolates from humans, United States, 1964–2004.
See this image and copyright information in PMC

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