Surveillance of legionellosis and Legionella bacteria in the built environment in Singapore.
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. 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 > or = 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 > or = 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 > or = 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 (52.6%) 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.
Heng
B H
BH
Quarantine & Epidemiology Department, Ministry of the Environment, Singapore.
Goh
K T
KT
Ng
D L
DL
Ling
A E
AE
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007875:Legionella / Q000302:isolation & purification; D007876:Legionellosis / Q000453:epidemiology* / Q000208:ethnology / Q000382:microbiology / Q000401:mortality; D007877:Legionnaires' Disease / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011159:Population Surveillance; D012846:Singapore / Q000453:epidemiology; D014504:Urban Health; D014871:Water Microbiology