A large outbreak of Legionnaires' disease at a flower show, the Netherlands, 1999

Emerg Infect Dis. 2002 Jan;8(1):37-43. doi: 10.3201/eid0801.010176.


In 1999, an outbreak of Legionnaires' disease affected many visitors to a flower show in the Netherlands. To identify the source of the outbreak, we performed an environmental investigation, as well as a case-control study among visitors and a serologic cohort study among exhibitors to measure exposure to possible sources. Of 77,061 visitors, 188 became ill (133 confirmed and 55 probable cases), for an attack rate of 0.23% for visitors and 0.61% for exhibitors. Two whirlpool spas in halls 3 and 4 of the exhibition and a sprinkler in hall 8 were culture positive for Legionella pneumophila. One of three genotypes found in both whirlpool spas was identical to the isolates from 28 of 29 culture-positive patients. Persons who paused at the whirlpool spa in hall 3 were at increased risk for becoming ill. This study illustrates that whirlpool spas may be an important health hazard if disinfection fails.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Antibodies, Bacterial / blood*
  • Case-Control Studies
  • Cohort Studies
  • Disease Outbreaks*
  • Female
  • Genotype
  • Humans
  • Hydrotherapy
  • Legionella pneumophila / classification
  • Legionella pneumophila / immunology*
  • Legionella pneumophila / isolation & purification
  • Legionnaires' Disease / epidemiology*
  • Male
  • Middle Aged
  • Netherlands / epidemiology
  • Risk Assessment
  • Seroepidemiologic Studies


  • Antibodies, Bacterial