Study based in Southern Ethiopia Purpose - to explore if children in contact with adults with TB have positive acute reactants such as IFN-y and other cytokine responses; if these responses discriminate between high and low risk of disease progression and whether these could be incorporated into improved diagnostic approaches.

The study follows children in contact with TB. Those with positive TST will be offered chemoprophylaxis and all children will be followed for 2 years to describe IFN-y responses over time, identify symptoms of active TB and if these symptoms are associated with IFN-y and other cytokine responses.

Children with suspicion of TB attending health centres will also be investigated using routine diagnostic tests and IFN-y and other cytokines responses to evaluate if the latter could be used in improved diagnostic approaches.

Inclusion Criteria:

- Children - 1 to 14 years old in contact with adults with smear positive TB

Or:

- Children with suspicion of TB admitted to the hospital for investigations

Exclusion Criteria:

- Residency > 10 Km from recruitment center

Or:

- Patient severely to undergo diagnostic procedures.