TB is treatable and curable. However, some people can develop resistance to the standard TB drugs. This can happen in several ways: when they don't complete the full course; when they are prescribed the wrong treatment, dose or length; when the drugs are not always available; or if the drugs are of poor quality. Sticking with multidrug-resistant TB treatment can be difficult due to the length of the treatment and complex combination of drugs, the expense, and the range of significant side-effects.
Drug-resistant TB (DR TB) is spread through the air from one person to another. It is estimated that in 2017, 558 000 people developed TB that was resistant to the most effective first-choice of drug (rifampicin,) and of these, 82% had developed multidrug-resistant TB (MDR-TB), which is resistant to at least two of the most potent anti-TB drugs (rifampicin and isoniazid). Another form of the disease, known as extensively drug-resistant TB (XDR-TB), is resistant to both these drugs and additional drugs used to treat MDR-TB.
DR-TB continues to be poorly detected and treated across the world, and cases of people with DR-TB are increasing. Three countries accounted for almost half of these 558 000 cases: India (24%), China (13%) and the Russian Federation (10%). Among cases of MDR-TB in 2017, 8.5% were estimated to have extensively drug-resistant TB.