[Five "W" in tuberculosis contact tracing: why, when, who, where, and what?]

The most successful intervention in tuberculosis control is early detection and early and effective treatment of tuberculosis patient. Therefore, identification of secondary cases and their prompt treatment may interrupt further transmission. This is the goal in the national tuberculosis programmes in high-incidence countries since extensive contact investigation is resource intensive. As countries approach the elimination phase of tuberculosis, more aggressive strategies are needed. Contact tracing is regarded as an effective intervention to identify and to treat recently infected persons and has become an essential component of the tuberculosis control and elimination strategies in most low-incidence countries. These activities can lead to the exhausting of the reservoir of future cases by preventing reactivation. Croatia is a middle--incidence country with decreasing incidence rates moving towards low-incidence situation. Contact investigation is an important part of tuberculosis control efforts. This study described current contact tracing principles and practice.