OUTBREAK OF DRUG-RESISTANT TUBERCULOSIS WITH 2ND-GENERATION TRANSMISSION IN A HIGH-SCHOOL CALIFORNIA

Background: In spring 1993, four students in a high school were diagno sed with tuberculosis resistant to isoniazid, streptomycin, and ethion amide. Methods: To investigate potential transmission of drug-resistan t tuberculosis, a retrospective cohort study with case investigation a nd screening by tuberculin skin tests and symptom checks was conducted in a high school of approximately 1400 students. Current and graduate d high-school students were included in the investigation, DNA fingerp rinting of available isolates was performed. Results: Eighteen student s with active tuberculosis were identified, Through epidemiologic and laboratory investigation, 13 cases were linked; 8 entered 12th grade i n fall 1993; 9 of 13 had positive cultures for Mycobacterium tuberculo sis with isoniazid, streptomycin, and ethionamide resistance, and all 8 available isolates had identical DNA fingerprints. No staff member h ad tuberculosis. One student remained infectious for 29 months, from J anuary 1991 to June 1993, and was the source case for the outbreak, An other student was infectious for 5 months before diagnosis in May 1993 and was a treatment failure in February 1994 with development of rifa mpin and ethambutol resistance in addition to isoniazid, streptomycin, and ethionamide. In the fall 1993 screening, 292 of 1263 (23%) studen ts tested had a positive tuberculin skin test. Risk of infection was h ighest among 12th graders and classroom contacts of the two students w ith prolonged infectiousness. An additional 94 of 928 (10%) students t ested in spring 1994 had a positive tuberculin skin test; 22 were clas sroom contacts of the student with treatment failure and 21 of these h ad documented tuberculin skin test conversions. Conclusion: Extensive transmission of drug-resistant tuberculosis was documented in this hig h school, along with missed opportunities for prevention and control o f this outbreak. Prompt identification of tuberculosis cases and timel y interventions should help reduce this public health problem.