Open Access Case report

Two Legionnaires' disease cases associated with industrial waste water treatment plants: a case report

Jaana Kusnetsov1*, Liisa-Kaarina Neuvonen2, Timo Korpio3, Søren A Uldum4, Silja Mentula5, Tuula Putus6, Nhu Nguyen Tran Minh7 and Kari-Pekka Martimo8

Author Affiliations

1 National Institute for Health and Welfare (THL), Water and Health Unit, P.O.Box 95, FI-70701 Kuopio, Finland

2 Medivire Occupational Health Care Center, Finland

3 UPM-Kymmene Oyj, Finland

4 Statens Serum Institut, Copenhagen, Denmark

5 National Institute for Health and Welfare, Bacteriology Unit, Helsinki, Finland

6 University of Turku, Turku, Finland

7 National Institute for Health and Welfare, Epidemiologic Surveillance and Response Unit, Helsinki, Finland

8 Mehiläinen Occupational Health Care, Helsinki, Finland

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BMC Infectious Diseases 2010, 10:343  doi:10.1186/1471-2334-10-343

Published: 2 December 2010



Finnish and Swedish waste water systems used by the forest industry were found to be exceptionally heavily contaminated with legionellae in 2005.

Case presentation

We report two cases of severe pneumonia in employees working at two separate mills in Finland in 2006. Legionella serological and urinary antigen tests were used to diagnose Legionnaires' disease in the symptomatic employees, who had worked at, or close to, waste water treatment plants. Since the findings indicated a Legionella infection, the waste water and home water systems were studied in more detail. The antibody response and Legionella urinary antigen finding of Case A indicated that the infection had been caused by Legionella pneumophila serogroup 1. Case A had been exposed to legionellae while installing a pump into a post-clarification basin at the waste water treatment plant of mill A. Both the water and sludge in the basin contained high concentrations of Legionella pneumophila serogroup 1, in addition to serogroups 3 and 13. Case B was working 200 meters downwind from a waste water treatment plant, which had an active sludge basin and cooling towers. The antibody response indicated that his disease was due to Legionella pneumophila serogroup 2. The cooling tower was the only site at the waste water treatment plant yielding that serogroup, though water in the active sludge basin yielded abundant growth of Legionella pneumophila serogroup 5 and Legionella rubrilucens. Both workers recovered from the disease.


These are the first reported cases of Legionnaires' disease in Finland associated with industrial waste water systems.