Tuberculosis outbreak among students in a boarding school

¹ Jerusalem District Health Office, Ministry of Health and Braun School of Public Health and Community medicine, Hebrew University, Hadassah Jerusalem, Israel
² Hadera Sub-District Health Office, Ministry of Health, Israel
³ Haifa District Health Office, Ministry of Health and the Faculty of Welfare and Health Science Haifa University, Israel
⁴ Tuberculosis clinic, Clalit Health Services, Hadera, Israel
⁵ National Mycobacteria Reference Center, Public Health Laboratories, Ministry of Health, Tel-Aviv Israel
⁶ Division of Respiratory physiology and chest diseases Carmel medical center, Haifa, Israel

^* To whom correspondence should be addressed. E-mail: chen{at}lbjer.health.gov.il.

	Abstract

Tuberculosis (TB) outbreaks present a public health challenge. Six cases of active tuberculosis emerged in a boarding school during one year. An epidemiological outbreak investigation was performed followed by implementation of control measures.

The investigation included interviews, tuberculin skin test (TST) and chest x-rays of the students. Close contact (n=155) was defined as being in the same class or dormitory with a patient. Remote contact (n=246) was defined as being in the school.

An epidemiologic association was detected among five of the cases and a distinct pattern was found in molecular analysis. TST was performed in 398 (99.2%) students. Repeated (two step) TST was applied to the close contacts. The degree of contact, country of origin and previous BCG vaccination were significantly (p<0.01) associated with TST reactions. Preventive directly observed therapy (DOT) was completed by 157 (91.3%) students. During five years follow up, no additional cases emerged.

While investigating a TB outbreak, the definition of degree of contact is a significant predictor for detecting positive tuberculin test. Immigration from an endemic country as well as previous BCG vaccination have a major effect on TST results. The DOT approach was found successful in preventing further morbidity.