title: Legionnaires' disease from a cooling tower in a community outbreak in Lidköping, Sweden- epidemiological, environmental and microbiological investigation supported by meteorological modelling.
abstract: BACKGROUND
  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.
  
  
  METHODS
  Classical epidemiological investigation, diagnostic tests, environmental analyses, epidemiological typing and meteorological methods.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Communicable Disease Control and Prevention, Region Västra Götaland SE-501 82, Borås, Sweden. peter.ulleryd@vgregion.se
authors.forename: Peter
authors.initials: P
authors.lastname: Ulleryd
authors.forename: Anna
authors.initials: A
authors.lastname: Hugosson
authors.forename: Görel
authors.initials: G
authors.lastname: Allestam
authors.forename: Sverker
authors.initials: S
authors.lastname: Bernander
authors.forename: Berndt E B
authors.initials: BE
authors.lastname: Claesson
authors.forename: Ingrid
authors.initials: I
authors.lastname: Eilertz
authors.forename: Anne-Christine
authors.initials: AC
authors.lastname: Hagaeus
authors.forename: Martin
authors.initials: M
authors.lastname: Hjorth
authors.forename: Agneta
authors.initials: A
authors.lastname: Johansson
authors.forename: Birgitta
authors.initials: B
authors.lastname: de Jong
authors.forename: Anna
authors.initials: A
authors.lastname: Lindqvist
authors.forename: Peter
authors.initials: P
authors.lastname: Nolskog
authors.forename: Nils
authors.initials: N
authors.lastname: Svensson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058491:Bacterial Load; D004196:Disease Outbreaks; D004783:Environmental Microbiology; D005260:Female; D006801:Humans; D016952:Legionella pneumophila / Q000145:classification / Q000302:isolation & purification*; D007877:Legionnaires' Disease / Q000453:epidemiology* / Q000382:microbiology; D008297:Male; D008685:Meteorological Concepts; D008875:Middle Aged; D058889:Molecular Typing; D012703:Serotyping; D013548:Sweden / Q000453:epidemiology