Limits...
Landscape epidemiology of tularemia outbreaks in Sweden.

Svensson K, Bäck E, Eliasson H, Berglund L, Granberg M, Karlsson L, Larsson P, Forsman M, Johansson A - Emerging Infect. Dis. (2009)

Bottom Line: Strong spatial associations were found between F. tularensis subpopulations and the places of disease transmission; infection by some subpopulations occurred within areas as small as 2 km(2), indicating unidentified environmental point sources of tularemia.In both locations, disease clusters were associated with recreational areas beside water, and genetic subpopulations were present throughout the tularemia season and persisted over years.High-resolution genotyping in combination with patients' statements about geographic places of disease transmission provided valuable indications of likely sources of infection and the causal genotypes during these tularemia outbreaks.

View Article: PubMed Central - PubMed

Affiliation: Swedish Defense Research Agency, Umea, Sweden.

ABSTRACT
Summer outbreaks of tularemia that occurred from 1995 through 2005 in 2 locations in Sweden affected 441 persons. We performed an epidemiologic investigation of these outbreaks using a novel strategy, involving high-resolution genotyping of Francisella tularensis isolates obtained from 136 patients (using 18 genetic markers developed from 6 F. tularensis genome sequences) and interviews with the patients. Strong spatial associations were found between F. tularensis subpopulations and the places of disease transmission; infection by some subpopulations occurred within areas as small as 2 km(2), indicating unidentified environmental point sources of tularemia. In both locations, disease clusters were associated with recreational areas beside water, and genetic subpopulations were present throughout the tularemia season and persisted over years. High-resolution genotyping in combination with patients' statements about geographic places of disease transmission provided valuable indications of likely sources of infection and the causal genotypes during these tularemia outbreaks.

Show MeSH

Related in: MedlinePlus

A) Cluster site for tularemia transmission at Oset/Rynningeviken nature reserve in Örebro, Sweden, with 83 patient reports. Twenty-seven Francisella tularensis isolates were recovered from these patients. B) Cluster site for tularemia transmission at Lake Lången, Örebro, Sweden, with 17 patient reports. Nine F. tularensis isolates were recovered from these patients. Place of disease transmission were reported to be certain (circle), probable (square), or possible (diamond); patient residency (triangle) was used if no such data was available. Genetic groups are indicated by color: yellow (1a), green (1b), blue (1d), or purple (2); white indicates no F. tularensis culture.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3044527&req=5

Figure 4: A) Cluster site for tularemia transmission at Oset/Rynningeviken nature reserve in Örebro, Sweden, with 83 patient reports. Twenty-seven Francisella tularensis isolates were recovered from these patients. B) Cluster site for tularemia transmission at Lake Lången, Örebro, Sweden, with 17 patient reports. Nine F. tularensis isolates were recovered from these patients. Place of disease transmission were reported to be certain (circle), probable (square), or possible (diamond); patient residency (triangle) was used if no such data was available. Genetic groups are indicated by color: yellow (1a), green (1b), blue (1d), or purple (2); white indicates no F. tularensis culture.

Mentions: Analysis per outbreak year showed that the number of patients with culture-verified tularemia were proportional to the total number of tularemia patients. The ages of patients from whom positive cultures were obtained ranged from 1 to 90 years, distributed evenly among age groups: 20%, 18%, 34%, and 28% in persons 0–20, 21–40, 41–60, and >60 years of age, respectively, with a male:female ratio of 1.2:1 (Appendix Tables 1, 2). No apparent correlations were found between genotypes and either the gender or age of the patients. The annual incidence rates of tularemia were 21–423 per 100,000 persons in the Municipality of Ljusdal and 12–55 per 100,000 persons in the County of Örebro in outbreak years, but disease-free years were interspersed between outbreaks. Generally, tularemia patients reported that they were infected at places used for outdoor activities, e.g., on walking paths, at bathing places, at golf courses, or in an allotment garden (parcels of land for cultivation) assigned to individuals or families (Figures 2–4; Technical Appendix). A statement of a likely arthropod transmission vector was available for patients from Örebro; indicating mosquitoes (n = 101), ticks (4), horse flies (8), mosquitoes or ticks (2), mosquitoes or horse flies (19); 144 patients reported not knowing (the vectors reported by the 80 patients with culture-verified tularemia are listed in Appendix Table 2). A presumed place of tularemia acquisition was pinpointed by 120 (88%) of 136 of patients and self-estimates of the quality of spatial data were available for 44 of 56 patients in Ljusdal and 76 of 80 patients in Örebro (Appendix Tables 1, 2) with culture-verified tularemia. Overall, patients felt confident about where they had acquired tularemia; 92 of 136 patients indicated that their place of disease acquisition was certain or probable (Table 2).


Landscape epidemiology of tularemia outbreaks in Sweden.

Svensson K, Bäck E, Eliasson H, Berglund L, Granberg M, Karlsson L, Larsson P, Forsman M, Johansson A - Emerging Infect. Dis. (2009)

A) Cluster site for tularemia transmission at Oset/Rynningeviken nature reserve in Örebro, Sweden, with 83 patient reports. Twenty-seven Francisella tularensis isolates were recovered from these patients. B) Cluster site for tularemia transmission at Lake Lången, Örebro, Sweden, with 17 patient reports. Nine F. tularensis isolates were recovered from these patients. Place of disease transmission were reported to be certain (circle), probable (square), or possible (diamond); patient residency (triangle) was used if no such data was available. Genetic groups are indicated by color: yellow (1a), green (1b), blue (1d), or purple (2); white indicates no F. tularensis culture.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3044527&req=5

Figure 4: A) Cluster site for tularemia transmission at Oset/Rynningeviken nature reserve in Örebro, Sweden, with 83 patient reports. Twenty-seven Francisella tularensis isolates were recovered from these patients. B) Cluster site for tularemia transmission at Lake Lången, Örebro, Sweden, with 17 patient reports. Nine F. tularensis isolates were recovered from these patients. Place of disease transmission were reported to be certain (circle), probable (square), or possible (diamond); patient residency (triangle) was used if no such data was available. Genetic groups are indicated by color: yellow (1a), green (1b), blue (1d), or purple (2); white indicates no F. tularensis culture.
Mentions: Analysis per outbreak year showed that the number of patients with culture-verified tularemia were proportional to the total number of tularemia patients. The ages of patients from whom positive cultures were obtained ranged from 1 to 90 years, distributed evenly among age groups: 20%, 18%, 34%, and 28% in persons 0–20, 21–40, 41–60, and >60 years of age, respectively, with a male:female ratio of 1.2:1 (Appendix Tables 1, 2). No apparent correlations were found between genotypes and either the gender or age of the patients. The annual incidence rates of tularemia were 21–423 per 100,000 persons in the Municipality of Ljusdal and 12–55 per 100,000 persons in the County of Örebro in outbreak years, but disease-free years were interspersed between outbreaks. Generally, tularemia patients reported that they were infected at places used for outdoor activities, e.g., on walking paths, at bathing places, at golf courses, or in an allotment garden (parcels of land for cultivation) assigned to individuals or families (Figures 2–4; Technical Appendix). A statement of a likely arthropod transmission vector was available for patients from Örebro; indicating mosquitoes (n = 101), ticks (4), horse flies (8), mosquitoes or ticks (2), mosquitoes or horse flies (19); 144 patients reported not knowing (the vectors reported by the 80 patients with culture-verified tularemia are listed in Appendix Table 2). A presumed place of tularemia acquisition was pinpointed by 120 (88%) of 136 of patients and self-estimates of the quality of spatial data were available for 44 of 56 patients in Ljusdal and 76 of 80 patients in Örebro (Appendix Tables 1, 2) with culture-verified tularemia. Overall, patients felt confident about where they had acquired tularemia; 92 of 136 patients indicated that their place of disease acquisition was certain or probable (Table 2).

Bottom Line: Strong spatial associations were found between F. tularensis subpopulations and the places of disease transmission; infection by some subpopulations occurred within areas as small as 2 km(2), indicating unidentified environmental point sources of tularemia.In both locations, disease clusters were associated with recreational areas beside water, and genetic subpopulations were present throughout the tularemia season and persisted over years.High-resolution genotyping in combination with patients' statements about geographic places of disease transmission provided valuable indications of likely sources of infection and the causal genotypes during these tularemia outbreaks.

View Article: PubMed Central - PubMed

Affiliation: Swedish Defense Research Agency, Umea, Sweden.

ABSTRACT
Summer outbreaks of tularemia that occurred from 1995 through 2005 in 2 locations in Sweden affected 441 persons. We performed an epidemiologic investigation of these outbreaks using a novel strategy, involving high-resolution genotyping of Francisella tularensis isolates obtained from 136 patients (using 18 genetic markers developed from 6 F. tularensis genome sequences) and interviews with the patients. Strong spatial associations were found between F. tularensis subpopulations and the places of disease transmission; infection by some subpopulations occurred within areas as small as 2 km(2), indicating unidentified environmental point sources of tularemia. In both locations, disease clusters were associated with recreational areas beside water, and genetic subpopulations were present throughout the tularemia season and persisted over years. High-resolution genotyping in combination with patients' statements about geographic places of disease transmission provided valuable indications of likely sources of infection and the causal genotypes during these tularemia outbreaks.

Show MeSH
Related in: MedlinePlus