TB is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air. A person needs to inhale only a few of these germs to become infected.

About one-third of the world’s population has latent TB, which means people have been infected by TB bacteria but are not (yet) ill with the disease and cannot transmit the disease.

People infected with TB bacteria have a 10% lifetime risk of falling ill with TB. However, persons with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco, have a much higher risk of falling ill.

When a person develops active TB disease, the symptoms (such as cough, fever, night sweats, or weight loss) may be mild for many months. This can lead to delays in seeking care, and results in transmission of the bacteria to others.

People with active TB can infect 10–15 other people through close contact over the course of a year. Without proper treatment, 45% of HIV-negative people with TB on average and nearly all HIV-positive people with TB will die.

Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis) that most often affect the lungs. Tuberculosis is curable and preventable.

Who is most at risk?

Tuberculosis mostly affects adults in their most productive years. However, all age groups are at risk. Over 25% of cases and deaths are in the African region.

People who are infected with HIV are 20 to 30 times more likely to develop active TB (see TB and HIV section below). The risk of active TB is also greater in persons suffering from other conditions that impair the immune system.

One million children (0–14 years of age) fell ill with TB, and 170 000 children (excluding children with HIV) died from the disease in 2015.
Tobacco use greatly increases the risk of TB disease and death. More than 20% of TB cases worldwide are attributable to smoking.

World TB Day celebrated on 24 March each year, is an opportunity to raise awareness about the burden of tuberculosis (TB) worldwide and the status of TB prevention and care efforts.

TB is the ninth leading cause of death worldwide and the leading cause from a single infectious agent, ranking above HIV/AIDS. Over 25% of TB deaths occur in the African Region.

The emergence of multidrug-resistant TB (MDR-TB) poses a major health security threat and could risk gains made in the fight against TB.

World TB Day provides the platform for affected persons and communities, civil society organizations, health-care providers, policy makers, development partners and others to advocate, discuss and plan further collaboration to fulfil the promise of reaching all people with quality TB prevention and care services, as well as enabling TB prevention through multisectoral development efforts.

https://www.afro.who.int/health-topics/tuberculosis-tb