Tuberculosis (TB) is still a huge problem throughout the world.
South Africa is particularly hard hit by the disease. It is one of only two countries where incidence of TB is still rising.
The problem is that many cases are now resistant to drug treatment, meaning some patients are being sent back home while they are still infectious.
Now a team at the University of Cape Town in South Africa is using new tools to investigate how the return of patients to their communities affects the spread of the disease.
Meera Senthilingam has been seeing the trial in action.
To watch the video on BBC News, click here.