Prevalence and risk factors for transmission of infection among children in household contact with adults having pulmonary tuberculosis

Aims: To study the prevalence of tuberculosis infection among children in household contact with adults having pulmonary tuberculosis, and identify the possible risk factors. Methods: Children under the age of 5 years who were in household contact with 200 consecutive adults with pulmonary tuberculosis underwent tuberculin skin testing. Transverse induration of greater than 10 mm was defined as positive tuberculin test suggestive of tubercular infection. Infected children underwent chest radiography and analysis of gastric lavage fluid or induced sputum for detection of acid fast bacilli. Results: Tuberculin test was positive in 95 of 281 contacts (33.8%), of which 65 were contacts of sputum positive patients, while 30 were contacts of sputum negative patients. Nine of these children were diagnosed as having tuberculosis based on clinical features and/or recovery of acid fast bacilli; seven were in contact with sputum positive adults. The important risk factors for transmission of infection were younger age, severe malnutrition, absence of BCG vaccination, contact with an adult who was sputum positive, and exposure to environmental tobacco smoke. Conclusion: The prevalence of tuberculosis infection and clinical disease among children in household contact with adult patients is higher than in the general population, and risk is significantly increased by contact with sputum positive adults.