ABSTRACT
<p><b>OBJECTIVE</b>To analyze the incidence of tuberculosis (TB) in people who were in close contact with smear-positive TB patients.</p><p><b>METHODS</b>A total of 19 159 subjects, including 17 334 family members and 1825 classmates of patients, in close contact with 6653 smear-positive TB patients in Shijiazhuang city from 2007 to 2008 were observed. All the classmates were tested by purified protein derivative (PPD) test and symptom screening, and all family members were screened by symptoms. All these subjects were trained with knowledge related to TB. The ones with positive PPD test and suspected TB symptoms were further examined by chest X-ray and sputum smear microscopy, and those without any symptom were followed up monthly throughout a two year period and were examined at any time if symptoms occurred.</p><p><b>RESULTS</b>A total of 281 patients with pulmonary TB were diagnosed in 2 years, including 176 family members and 105 classmates in all close contacts. The smear-positive incidences were 1466.67/100 000. The incidences for 14 - 25 years old group and more than 75 years old group were 2907.18/100 000 (83/2855) and 2650.96/100 000 (18/679), which were higher than those for other groups. Two higher incidences were related to close contact time periods of 6 months (929.07/100 000, 178/19 159) and 13 - 18 months (369.12/100 000, 70/18 964). Three highest incidences were observed in the roommates (11 384.62/100 000, 37/325), classmates (4533.33/100 000, 68/1500) and couples (1624.17/100 000, 86/5295).</p><p><b>CONCLUSION</b>Closer contact with smear-positive patients with TB may result in the higher chance of TB. Close contact for 6 months or 13 to 18 months caused more patients, and the 14 - 25 years old group and more than 75 years old group had higher incidences of TB.</p>