TB is difficult to diagnose - the bacteria grow slowly, and thus do severity of symptoms. And it is difficult to treat - the bacteria wrap themselves in a waxy sheath, which stops the drugs getting through so they have to be taken over a long period, and the drugs have unpleasant side effects, so people don't like taking the long courses. It's spread by people living in close proximity for quite long periods, such as may be the result of living in poverty.<p>This all makes it very difficult/impossible to eradicate.<p>Speaking as an ex TB lab technician, but not for a long time past.