**6. Future studies**

#### **Future Studies on Epidemiology**

In all epidemiological studies it is essential to have a clear definition of a case of the disease being investigated by delineating the symptoms, signs or other characteristics indicating that a person has the disease. A clear definition of an exposed person is also necessary. This definition must include all the characteristics that identify a person as being exposed to the factor in question. In the absence of clear definitions of disease and exposure, it is very difficult to interpret the data from an epidemiological study.

#### **Future Studies on Transmission of TB**

Future epidemiological studies on the transmission of drug-resistant TB should incorporate more comprehensive strain data, including specific drug resistance-conferring mutations and information on the strain genetic background. These variables, as well as their interaction, could play an important role in the transmission success of particular drug-resistant variants.

#### **Future Studies on HIV/TB**

The investigators who conduct the studies on HIV/ TB need to consider other possible risk factors for drug resistance such as demographics; prior therapy, socioeconomic status, and quality of TB control programs, etc.
