Legionnaires’ disease from a cooling tower in a community outbreak in Lidköping, Sweden- epidemiological, environmental and microbiological investigation supported by meteorological modelling
1 Department of Communicable Disease Control and Prevention, Region Västra Götaland SE-501 82, Borås, Sweden
2 Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
3 Department of Medicine, Lidköping Hospital, Lidköping, Sweden
4 Department of Diagnostics and Vaccinology, Swedish Institute for Communicable Disease Control, Solna, Sweden
5 Section of Clinical Microbiology, Department of Medical Sciences, Uppsala University Hospital, Uppsala, Sweden
6 Department of Clinical Microbiology, Skövde Hospital, Skövde, Sweden
7 Department of Veterinary, County Administrative Board, Västra Götaland, Sweden
8 Department of Environmental Health Office, Community of Lidköping, Lidköping, Sweden
9 Department of Surveillance and Response Support, European Centre for Disease Prevention and Control, Stockholm, Sweden
10 Department of Infectious Disease, Skövde Hospital, Skövde, Sweden
11 At the time the study was conducted: Department of Epidemiology, Swedish Institute for Infectious Disease Control, Solna, Sweden
BMC Infectious Diseases 2012, 12:313 doi:10.1186/1471-2334-12-313Published: 21 November 2012
An outbreak of Legionnaires’ Disease took place in the Swedish town Lidköping on Lake Vänern in August 2004 and the number of pneumonia cases at the local hospital increased markedly. As soon as the first patients were diagnosed, health care providers were informed and an outbreak investigation was launched.
Classical epidemiological investigation, diagnostic tests, environmental analyses, epidemiological typing and meteorological methods.
Thirty-two cases were found. The median age was 62 years (range 36 – 88) and 22 (69%) were males. No common indoor exposure was found. Legionella pneumophila serogroup 1 was found at two industries, each with two cooling towers. In one cooling tower exceptionally high concentrations, 1.2 × 109 cfu/L, were found. Smaller amounts were also found in the other tower of the first industry and in one tower of the second plant. Sero- and genotyping of isolated L. pneumophila serogroup 1 from three patients and epidemiologically suspected environmental strains supported the cooling tower with the high concentration as the source. In all, two L. pneumophila strains were isolated from three culture confirmed cases and both these strains were detected in the cooling tower, but one strain in another cooling tower as well. Meteorological modelling demonstrated probable spread from the most suspected cooling tower towards the town centre and the precise location of four cases that were stray visitors to Lidköping.
Classical epidemiological, environmental and microbiological investigation of an LD outbreak can be supported by meteorological modelling methods.
The broad competence and cooperation capabilities in the investigation team from different authorities were of paramount importance in stopping this outbreak.