Tuberculosis (TB) is one of the top causes of death worldwide, and millions of people continue to fall ill and suffer from the effects of TB each year. TB caused an estimated 1.4 million deaths in 2018, and an estimated ten million people were newly infected with TB. Of those people, around 40% are ‘missed’: that is, they are not diagnosed, reported to a health system, or treated. A person with active, untreated TB can spread the disease to as many as 15 other people in a year, which makes it all the more urgent to find and care for these missing people.
Over 25% of the world’s population is infected with latent TB, and at risk of progressing to active TB at any time if they are not identified and provided with prevention therapy. It is also estimated that in 2017, 558 000 people globally 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 more than one of the recommended drugs.
Of the ten million people who developed TB disease in 2017, most are men (5.8 million), 3.2 million women, and one million are children (aged below 15). Vulnerable populations are especially at risk of TB. They include people living with HIV (9%), people who use drugs, mobile and migrant populations, prisoners, miners and indigenous people.
Among major known risk factors for TB, HIV infection is the strongest. Around 25% of all TB-related deaths occur in HIV-positive individuals, with the majority (75%) of HIV-associated active TB disease cases and deaths occurring in Africa. An estimated 27% of TB cases worldwide are attributable to undernutrition and 22% to indoor air pollution. Other risk factors for TB include type-2 diabetes mellitus, excessive alcohol use (both of which roughly triple the risk of TB), and smoking (which doubles the risk).