Additional risk of developing TB for household members with a TB case at home at intake: a 15-year study.
OBJECTIVE
To assess the additional risk to household contacts from an infectious case of tuberculosis (TB) at home in a rural community in south India.


METHODS
In all, 3506 contacts of smear-positive (S+C+) and 2910 contacts of smear-negative TB cases (S-C+) and 246 845 persons with no TB case at home were followed for 15 years, with a repeat survey every 2.5 years consisting of radiographic and sputum examination, selective follow-up of high-risk individuals and passive surveillance. If a case developed during follow-up, all household members were subsequently considered as contacts. Cox's proportional hazards model (multivariate) was employed to compare incidences.


RESULTS
The annual incidence of culture-positive TB was respectively 526 and 271 per 100000 population for contacts of smear-positive and smear-negative patients, and 198/100000 in non-contacts. The adjusted hazard rate was 3.4 for contacts of smear-positive patients (95% CI 3.0-3.9) and 1.7 for contacts of smear-negative patients (95% CI 1.4-2.0) as compared to non-contacts. Of 3942 incident cases, 337 (8.5%) came from households with a TB case.


CONCLUSIONS
Although family contacts had a significantly higher incidence, their contribution to total new caseload was meagre. Contact chemoprophylaxis as a public health measure would therefore have limited impact on community TB incidence.
Radhakrishna
S
S
Tuberculosis Research Centre, Chennai, India.
Frieden
Thomas R
TR
Subramani
R
R
Santha
T
T
Narayanan
P R
PR
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004311:Double-Blind Method; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007194:India / Q000453:epidemiology; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance / Q000379:methods; D015995:Prevalence; D016016:Proportional Hazards Models; D012307:Risk Factors; D012424:Rural Population; D014397:Tuberculosis, Pulmonary / Q000453:epidemiology / Q000635:transmission*