Prevalence of tuberculosis infection in Melbourne secondary school students.

OBJECTIVE: To estimate the prevalence of asymptomatic Mycobacterium tuberculosis infection in Melbourne secondary school students. DESIGN: Cross-sectional Mantoux testing of a partly random and partly targeted sample of secondary school students, designed to enable estimation of prevalence by region of birth. SETTING: Fifty-one State and Catholic secondary schools in metropolitan Melbourne during 1995. PARTICIPANTS: Australian and overseas-born students in Years 9 and 10. OUTCOME MEASURES: Proportions of students with positive Mantoux reactions (defined as induration at 48 hours of > or = 5 mm with a history of recent exposure; > or = 10 mm and no prior BCG vaccination; > or = 15 mm and prior BCG vaccination). RESULTS: Of 2586 students potentially eligible for testing, evaluable results were obtained from 1274 (49%). The overall prevalence of infection for Melbourne students in Years 9 and 10 was 2.5% (95% CI, 1.1-3.9%). Main predictors of a positive test were birth overseas and number of years residing overseas. Prevalence varied considerably by region of birth, and was very low in students born in Australia (0.7%), "other developed countries" (0.7%), and Southern Europe (0). The highest rates were observed in students born in Indochina (15.9%), other countries in South East Asia (10.2%), and Eastern Europe (10.2%). CONCLUSIONS: The risk of a young person becoming infected with M. tuberculosis while living in Melbourne is very low. Our results do not indicate a need for the reintroduction of mass screening in Victorian schools. If targeted screening were to be considered, the group most likely to benefit would be recently arrived migrants from Indochina.

High rate of transmission of tuberculosis in an office: impact of delayed diagnosis.

We identified two cases of tuberculosis (TB) in office co-workers in Melbourne, Victoria, Australia; the Mycobacterium tuberculosis isolates were found to be identical with use of restriction fragment length polymorphism. Contact tracing was performed for 195 of 210 workers by means of the tuberculin skin test. Risk of infection was assessed according to a number of variables. Office contacts were exposed to infectious TB for 4 months; at least 24% of employees were infected. There was an association between sitting in proximity to the case during the period of exposure (OR, 4.24; 95% CI, 1.06-19.67). On-site workers had a higher risk of being infected (OR, 5.48; CI, 1.51-23.54) than did visiting workers. Workers in this office were exposed to open pulmonary TB for prolonged periods. The prevalence of TB infection (24%) among these workers was high compared with the infection rate (2%-7%) in the general community. Delay in diagnosis was the major factor responsible for the spread of TB in this office.