Before the discovery of specific antibiotics for the treatment of tuberculosis, there was no cure. Mortality of those with pulmonary disease (disease of the lungs) was about 50%. The introduction of anti-tuberculosis drugs in the 1950s and the development of the various drug regimens meant that by the 1980s there was a 98% chance of cure. However, treatment had to be continued with good quality drugs for as long six months to ensure cure. The difficulties in ensuring this occurs, especially in resource poor countries, has resulted in an increasing incidence of tubercle bacteria resistant to the most effective drugs; so called multi-drug resistant tuberculosis.