High frequency of Tuberculosis in households of patients with Pulmonary Tuberculosis in Mzimba, Malawi.

A case-control study was carried out in Mzimba district to determine whether household members of a patient with pulmonary tuberculosis (PTB) had an increased frequency of TB compared with households where no TB had been previously diagnosed. There were 79 patients with PTB (66 with smear-positive PTB and 13 with smear-negative PTB) and 79 controls, matched by age and sex. Household compositions were similar. During a mean period of observation of 35 months, 8 household members from PTB patient households developed TB compared with no household members from control households (RR 1.99, 95% CI 1.81 - 2.18). The case notification rate of TB in household members from patients with all types of PTB was calculated at 1221 / 100.000/ year: the rates were 1233 /100,000 / year for household members from patients with smear-positive PTB and 1127 for household members from patients with smear-negative PTB. The frequency of TB in households of TB patients is significantly higher than in households of control persons who have not suffered from TB.