LEGIONELLOSIS LINKED WITH A HOTEL CAR PARK - HOW MANY WERE INFECTED

An outbreak of legionellosis associated with a hotel in Sydney, Austra lia, and the subsequent epidemiological and environmental investigatio ns are described. Four cases of Legionnaires' disease were notified to the Public Health Unit. A cross-sectional study of 184 people who att ended a seminar at the hotel was carried out. Serological and question naire data were obtained for 152 (83%) of these. Twenty-eight (18%) re spondents reported symptoms compatible with legionellosis. Thirty-thre e subjects (22%) had indirect fluorescent antibody (IFA) titres to Leg ionella pneumophila serogroup 1 (Lp-l) of 128 or higher. The only site which those with symptoms of legionellosis and IFA titre greater than or equal to 128 were more likely to have visited than controls was th e hotel car park (adjusted odds ratio [OR] 14.7, 95% confidence interv al [CI]: 1.8-123.1). Those with symptoms compatible with legionellosis , but whose IFA titres were < 128 were also more likely to have visite d the hotel car park (adjusted OR 4.4, 95% CI: 1.5-12.9). Seroprevalen ce of Lp-l antibodies was higher in those who attended the seminar tha n in a population sample of similar age. Findings suggested that the 4 cases represented a small fraction of all those infected, and highlig hted difficulties in defining illness caused by Lp-l and in interpreti ng serology.