During the period 1986 to 1996, a total of 258 sporadic cases of community-acquired legionellosis was reported, giving a mean annual morbidity rate of 0.9 per 100,000 population. The majority of the cases (91.5%) was serologically diagnosed by the indirect fluorescent antibody (IFA) test against Legionella pneumophila based on single sera with a titre of ≥1:1024. The others were confirmed by a four-fold increase in IFA titre to a minimum of 1:128 (7.4%) and by culture (1.1%). Cases were reported predominantly among males, ethnic Indians, the elderly, and those with concurrent medical conditions. The overall case-fatality rate was 14.7%, with the rate significantly higher among those aged ≥45 years (21%), smokers (20.4%), and those with concurrent medical conditions (22.5%). Seroepidemiological studies among the healthy population based on an IFA titre of ≥1:32 showed a prevalence of between 10.3% and 21.9%. Of the various occupational groups investigated, high seroprevalence rates were found in foreign construction workers (52.4%) and occupants of a building investigated for an unusual building-related illness (76.1%). Environmental surveillance of Legionella bacteria showed that 36% of cooling towers, 15% to 19% of decorative fountains and waterfalls, and 2% of spa pools were positive. The majority (85%) of environmental isolates was identified as Legionella pneumophila: 54.8% of serogroup 1 and 5% of Pontiac subtype.
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Declaration
The author(s) declare there are no affiliations with or involvement in any organisation or entity with any financial interest in the subject matter or materials discussed in this manuscript.
