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Home Eurosurveillance Weekly Release  2003: Volume 7/ Issue 33 Article 4
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Eurosurveillance, Volume 7, Issue 33, 14 August 2003

Citation style for this article: Penttinen P, Giesecke J. Outbreak of tularaemia in Sweden, July-August 2003. Euro Surveill. 2003;7(33):pii=2276. Available online:

Outbreak of tularaemia in Sweden, July-August 2003

Pasi Penttinen ( and Johan Giesecke (, Department of Epidemiology, Swedish Institute for Infectious Disease Control, Solna, Sweden.

Between 1 July and 11 August, 109 cases of tularaemia (Francisella tularensis var holarctica) were notified to the Swedish Institute of Infectious Diseases (Smittskyddsinstitutet, SMI) (Figure 1). Sixty per cent of cases are in men and most of the cases have occurred in people of active working age (Table 1). Typically, most cases are clustered tightly by geography. The locations and the total number of cases vary markedly from year to year (Figure 2).

Table 1. Age and sex distribution of notified tularaemia cases in Sweden between 1 July to 8 August 2003

Age Female Male Total
0-9 years 1 9 10
10-19 years 2 6 8
20-29 years 3 3 6
30-39 years 6 8 14
40-49 years 7 16 23
50-59 years 13 11 24
60-69 years 9 10 19
70+ years 3 2 5
Total 44 65 109


Figure 1. Number of notified tularaemia cases by week of notification, Sweden, 1 July to 11 August 2003. *Only one day (11 August) of week included. Source: SMI.


Figure 2. Number of tularaemia notifications by year, Sweden, 1997 - 2002.

The ulcero-glandular form of the disease dominates, with most cases reporting a mosquito or tick bite at the site of the ulcer and subsequent lymphadenopathy. This is consistent with the presentation during previous years in Sweden (1). This year, a few clusters with respiratory disease probably due to inhalational exposure have also been reported. These cases are typically in farmers, with onset of disease within a few days of working with hay. Similar inhalational exposure of farmers has been reported from previous outbreaks in Sweden and Finland (2,3). Depending on the route of exposure, tularaemia may also present in the oculoglandular and oropharyngeal forms (4).

In addition, F. tularensis has also been diagnosed in post mortem analyses of three hares from one of the affected counties by the National Veterinary Institute (Statens Veterinärmedicinska Anstalt, SVA) (5). Reports of dead hares, voles, and other small rodents around the areas with human cases have been included in many case notifications. The reservoir of F. tularensis in nature is unknown, although its survival in water and mud together with the apparent distribution along lakes and rivers in Sweden and eastern Europe is suggestive of a water associated reservoir (4).

Mosquito bites, owning a cat, farming, and visiting wooded areas were identified as independent risk factors for tularaemia in a recent Swedish case-control study (1). In this study, 16% of the cases were admitted to hospital. Tularaemia is responsive to antibiotic treatment, if begun within one week of onset of disease. With adequate treatment, mortality due to infection with F. tularensis var holarctica is very low. No deaths due to tularaemia in Sweden have been reported to SMI during this season.

The early start of tularaemia notifications together with the rapid increase in number of notifications during the first weeks suggest an epidemic year in Sweden. Despite the proximity of some of the affected areas to the Norwegian border, no cases had been notified in Norway by 11 August (6). In Finland, dozens of cases have been reported from the areas affected
during the 2000 epidemic (7).

Tularaemia continues to warrant vigilance during late summer and early autumn in the Nordic countries. Early identification of case clusters is useful for correct clinical management of cases. Research is needed to identify the natural reservoir and other environmental factors contributing to annual changes in incidence. Natural early warning signals might even allow preventive measures in affected geographical areas.

  1. Eliasson H, Lindbäck J, Nuorti JP, Arneborn M, Giesecke J, Tegnell A. The 2000 Tularemia Outbreak: Study of Risk Factors in Disease-Endemic and Emergent Area, Sweden. Emerg Infect Dis 2002; 9: 956-60. (
  2. Dahlstrand S, Ringertz O, Zetterberg B. Airborne tularemia in Sweden. Scand J Infect Dis 1971; 3: 7-16.
  3. Syrjälä H, Kujala P, Myllylä L, Salminen A. Airborne transmission of Tularemia in Farmers. Scand J Infect Dis 1985; 17: 371-5.
  4. Tärnvik A, Berglund L. Tularaemia. Eur Respir J 2003; 21: 361-73
  5. Statens Veterinärmedicinska Anstalt. Aktuellt om harpest. News item, 4 August 2003. [in Swedish] ( [accessed 14 August 2002]
  6. Nygård K, Brantsæter A. Tularemi (Harepest) [in Norwegian]. MSIS-rapport 2003; 31(32) ( [accessed 14 August 2002]
  7. Finnish online registry for infectious disease notifications. National Public Health Institute (KTL) ( [accessed 14 August 2003]

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