Tuberculosis (TB) is an infectious disease usually caused by Mycobacterium tuberculosis (MTB) bacteria. Tuberculosis generally affects the lungs but can also affect other parts of the body. Most infections do not have symptoms, in which case it is known as latent tuberculosis. About 10% of latent infections progress to active disease which, if left untreated, kills about half of those affected. The classic symptoms of active TB are a chronic cough with blood-containing mucus, fever, night sweats, and weight loss. It was historically called “consumption” due to the weight loss. Infection of other organs can cause a wide range of symptoms. Tuberculosis is spread through the air when people who have active TB in their lungs cough, spit, speak, or sneeze. People with latent TB do not spread the disease. Active infection occurs more often in people with HIV/AIDS and in those who smoke. TB is a leading killer of HIV-positive people. Diagnosis of active TB is based on chest X-rays, as well as microscopic examination and culture of body fluids. Diagnosis of latent TB relies on the tuberculin skin test (TST) or blood tests.
Prevention of TB involves screening those at high risk, early detection and treatment of cases, and vaccination with the bacillus Calmette-Guérin (BCG) vaccine. Those at high risk include household, workplace, and social contacts of people with active TB. Treatment requires the use of multiple antibiotics over a long period of time. Antibiotic resistance is a growing problem and health security threat with increasing rates of multiple drug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB). MDR-TB is treatable and curable by using second-line drugs. However, second-line treatment options are limited and require extensive chemotherapy (up to 2 years of treatment) with medicines that are expensive and toxic. Ending the TB epidemic by 2030 is among the health targets of the Sustainable Development Goals.
As of 2018 one-quarter of the world’s population is thought to be infected with TB. New infections occur in about 1% of the population each year. In 2017, there were more than 10 million cases of active TB which resulted in 1.6 million deaths, including 0.3 million among people with HIV. This makes it the number one cause of death from an infectious disease. More than 95% of deaths occurred in developing countries, and more than 50% in India, China, Indonesia, Pakistan, and the Philippines. About 80% of people in many Asian and African countries test positive while 5–10% of people in the United States population test positive by the tuberculin test. An estimated 54 million lives were saved through TB diagnosis and treatment between 2000 and 2017. WHO estimates that there were 558 000 new cases with resistance to rifampicin – the most effective first-line drug, of which 82% had MDR-TB. In 2017, an estimated 1 million children became ill with TB and 230 000 children died of TB (including children with HIV associated TB).
