Estimation of serial interval and incubation period of tuberculosis using DNA fingerprinting

OBJECTIVE: To determine the frequency distributions of serial interval and incubation period of tuberculosis within 4 years of transmission, and to identify correlates of serial intervals and incubation periods.METHODS: DNA fingerprints were obtained for all isolates from all culture-positive patients notified in The Netherlands from 1993 to 1996. Patient information was obtained from the National Tuberculosis Register. Results from contact investigations were provided by public health services. Source cases and secondary cases of tuberculosis were identified, based on 1) identical DNA fingerprints, and 2) epidemiological confirmation of contact. Under-representation of long intervals were corrected for by weighting cases.RESULTS: A total of 69 source-secondary case couples were identified. The geometric mean serial interval was 29.5 weeks (95% confidence interval [CI] 22.8-38.2 weeks) and the geometric mean incubation period 20.8 weeks (95% CI 15.5-27.8 weeks). Serial intervals and incubation periods tended to increase with age (P > 0.05). Three secondary cases with human immunodeficiency virus infection showed very short incubation periods (P > 0.05).CONCLUSION: Using a new methodology, the distribution of incubation periods of tuberculosis gave results consistent with earlier studies.