The source of infection to a child is usually an adult, often a family member with sputum smear positive tuberculosis. The frequency of childhood TB in a given population depends on-

1. The number of infectious cases.

2. Closeness of contact with an infectious case.

3. The age of child when exposed to TB and the age structure of the population.

Children rarely have sputum smear positive TB & it is unlikely that they are a powerful source of transmission of TB. Tuberculosis in children is mainly due to failure of TB control in adults. The risk of infection to a child depends on extent of exposure to infectious droplet nuclei. An infant whose mother has sputum smear positive TB has a high chance of becoming infected. The chance of developing disease is greatest shortly after infection and steadily decreases as the time goes by.

Because of less developed immune system, children under five years of age are more prone to develop the disease mostly within 2 years following infection. The commonest age of childhood TB disease is 1 to 4 years. Young age is a risk factor for spread of disease to other parts of body, i.e, dissemination. Most children are sputum smear-negative and infectious to others.The diagnosis of TB is particularly difficult in children because they rarely cough up sputum. As there are no specific features on clinical examination to confirm that the presenting illness is due to TB, look for clues to TB in children such as contact with an adult an older child with smear positive TB, failure to thrive or weight loss, and respiratory symptoms such as cough lasting more than three weeks in a child who has received a course of broad spectrum antibiotics. If available, a tuberculin skin test should be done, as it may provide suppurative evidence. A negative tuberculin skin test should be done, as it may provide suppurative evidence. A negative tuberculin test does not exclude TB. Chest x-ray is commonest investigation in suspected TB or miliary TB.

A symptomatic child contact with a positive Mantoux test is to be treated as case, regardless of whether or not has been given BCG vaccination in the past. For infants, if the mother or any other household member is smear-positive, then chemoprophylaxis should be given for three months. Then do a Mantoux test. If Mantoux test is negative, stop chemoprophylaxis and give BCG. If test is positive, continue chemoprophylaxis for a total duration of 6 months.