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. 2015 Jan;21(1):32-9.
doi: 10.3201/eid2101.140916.

Epidemiology and ecology of tularemia in Sweden, 1984-2012

Amélie Desvars, Maria Furberg, Marika Hjertqvist, Linda Vidman, Anders Sjöstedt, Patrik Rydén, Anders Johansson

Epidemiology and ecology of tularemia in Sweden, 1984-2012

Amélie Desvars et al. Emerg Infect Dis. 2015 Jan.

Abstract

The zoonotic disease tularemia is endemic in large areas of the Northern Hemisphere, but research is lacking on patterns of spatial distribution and connections with ecologic factors. To describe the spatial epidemiology of and identify ecologic risk factors for tularemia incidence in Sweden, we analyzed surveillance data collected over 29 years (1984-2012). A total of 4,830 cases were notified, of which 3,524 met all study inclusion criteria. From the first to the second half of the study period, mean incidence increased 10-fold, from 0.26/100,000 persons during 1984-1998 to 2.47/100,000 persons during 1999-2012 (p<0.001). The incidence of tularemia was higher than expected in the boreal and alpine ecologic regions (p<0.001), and incidence was positively correlated with the presence of lakes and rivers (p<0.001). These results provide a comprehensive epidemiologic description of tularemia in Sweden and illustrate that incidence is higher in locations near lakes and rivers.

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Figures

Figure 1
Figure 1
Mean incidence of tularemia (per 100,000 persons) and number of local outbreaks, Sweden, 1984−2012.
Figure 2
Figure 2
Annual mean incidence of tularemia by age group and sex, Sweden, 1984−2012. Asterisks (*) indicate significant differences by sex.
Figure 3
Figure 3
Cumulative number of tularemia cases, by week of onset, Sweden, 1984−2012.
Figure 4
Figure 4
Distribution of 3,524 tularemia cases, Sweden, 1984−2012. Red dots indicate locations of reported cases; blue line indicates border between northern and southern Sweden, as defined by the southern border of the boreal forest. The municipalities with the highest tularemia incidence (Ljusdal, Malung, Ockelbo), and most outbreaks (Örebro) are indicated, as is the capital city of Stockholm.
Figure 5
Figure 5
Mean incidence (per 100,000 persons) of tularemia in 189 municipalities by 5-year* intervals, Sweden, 1984−2012. *Most recent interval, 2009–2012, was 4 years.
Figure 6
Figure 6
Distribution of tularemia cases by ecologic region, Sweden, 1984−2012. Black dots indicate locations of reported cases. Region designations adopted from (24).
Figure 7
Figure 7
Distribution of tularemia cases by altitude, Sweden, 1984−2012. Black dots indicate locations of reported cases.
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