TB is an airborne infectious disease thought to infect almost one-third of the world's population. It commonly manifests as an infection of the lungs, usually with symptoms of coughing, weight loss and other constitutional symptoms. TB spreads easily and quickly and thus the increased travel generated by globalization may aid its spread. TB is the largest single infectious cause of death among young people and adults today and accounts for more than one-quarter of all preventable adult deaths in developing countries. The economic impact is high owing to the size of the problem and the fact that, in the poorest countries, the majority of those affected are economically active.
Every year, 2 to 3 million people die of TB and 8 million develop active infections. There are 1.6 million TB cases a year in sub-Saharan Africa, 3 million a year in South-East Asia and 0.33 million per year in Eastern Europe (0.36 including Turkey). Some 95% of cases and 98% of TB deaths occur in poor countries and numbers are rising owing to the growing HIV/AIDS epidemic.
Globally, 79% of people with TB do not have access to directly observed therapy short-course (DOTS), which is the recommended treatment. It is estimated that the introduction of the DOTS strategy could halve a country's current national economic loss from TB.
Until 50 years ago, there were no medicines to cure TB. Today strains of TB with anti-microbial resistance have emerged and there is evidence that poorly managed and financed TB programmes are exacerbating the problem and threatening to make TB incurable. Up to 50 million people may be infected with drug-resistant TB. There is no affordable cure for developing countries for some multi-drug-resistant (MDR) strains, defined as resistant to the two most important drugs, isoniazid and rifampicin.
Resistance is caused by inconsistent or partial treatment: when patients do not take all the medicines regularly for the required period because they start to feel better, doctors and health workers prescribe the wrong drugs or the wrong combination of drugs, or the drug supply is unreliable. Drug-resistant TB is more difficult and more expensive to treat and more likely to be fatal. In industrialized countries, TB treatment costs about US$2 000 a patient, but rises more than hundredfold to up to US$250 000 a patient with anti-microbial resistant TB.