Serological findings and health complaints inexhibitors working on the 1999 Westfriese Flora in Bovenkarspel. A study following the outbreak of Legionnaires'Disease in visitors of the Westfriese

This study was aimed at contributing to finding the source of a epidemic of Legionnaire's disease (LD) in visitors of the Westfriese Flora 1999 (West-Frisian Flower-show). The Westfriese Flora is a yearly flower exhibition combined with an agricultural and consumer products fair. The study targeted all persons without LD who had been working on the Westfriese Flora as volunteer, employee to the exhibition-organization or exhibitor. These persons were asked to fill in a questionnaire on their health status before and after the exhibition and their whereabouts during the exhibition. They were also asked to have a paired blood-sample taken to be tested for antibodies against L. pneumophila. No clear relations between health complaints and specific places or other factors, like drinking tap-water, were seen. However, antibody levels were clearly increased in those working in hall 3, but not in those working at other places and therefore the main LD spreading source should be sought in hall 3. The exact location, however, can not be inferred from this study with any certainty. From the two potential sources in hall 3 (a whirlpoolspa and a bubblemat) our data seem to indicate the whirlpoolspa as the more likely source, but this is not conclusive. From these findings we conclude that exposure to L. pneumophila seems to cause a slight elevation of antibody titers in those who do not develop LD, but that this increase is not accompanied by a demonstrable amount of milder forms of disease (apart from LD).