Children can present with TB at any age, but the most common age is between one and four years. In most cases, TB in children is a result of primary TB (i.e. the first infection) from an infectious adult or older child, unlike cases in adults which are most often due to reactivation of a previous TB infection. The best way to prevent childhood TB is therefore by proper identification of those who may be infected with TB, and treatment of active TB patients in the home and community.

The HIV epidemic has made the position with regard to TB worse by increasing the risk of reactivation of latent TB infection and by facilitating more rapid progression of TB disease. TB can readily be transmitted to both HIV-negative and HIV-positive households and to other close contacts of infectious patients.