Tuberculosis transmission in the family.

OBJECTIVE

To evaluate the risk of tuberculosis (TB) transmission from family members with infectious TB to other family members, and to examine whether household contact investigations had an impact on tuberculosis patterns.

DESIGN

Under the direction of the Taipei Municipal Chronic Disease Hospital, 12 full-time public health nurses recruited the household contacts of TB patients. Chest X-ray examination was recommended for adult contacts. Child contacts received the Mantoux tuberculin skin test, and radiography was recommended if the results were positive.

SETTING

Family contacts of all TB index patients who attended one of 29 hospitals in Taipei, from July 1993 through June 1996. The medical records of index patients were obtained from the National Tuberculosis Registry.

RESULTS

During the study period, the families of 3903 index patients, comprising 11873 contacts, were investigated. Among these, 4595 received radiography, for a response rate of 38.7%. Of these, 284 had active pulmonary disease: 188 (66.3%) had minimal disease, 79 (27.8%) had moderately advanced disease, and only 17 (5.9%) had far advanced disease. Overall, the index patients had more advanced TB: only 1261 (32.3%) had minimal disease, while 2022 (51.8%) had moderately advanced disease and 620 (15.9%) had far advanced disease.

CONCLUSIONS

These data show a relatively high risk of intrafamily TB transmission. Our findings also show that family contact investigations may help to diagnose TB in earlier stages. Such an approach should greatly reduce the number of new TB cases and speed eradication of the disease.