Tuberculosis (TB) is a contagious bacterial infection caused by Mycobacterium tuberculosis that primarily affects the lungs and is spread through the air from person to person by droplets. Infection occurs by inhaling these droplets after an infected person coughs, sneezes, speaks, sings, or laughs. People nearby may breathe in these bacteria and become infected. People with TB disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers, or schoolmates. Anyone can get tuberculosis, but risk increases with close or prolonged contact with a person with active TB disease or presence of a health problem that weakens the immune system.
About one quarter of the world's population is infected with Mycobacterium tuberculosis and thus are at risk of developing TB disease. In 2018, an estimated 10 million people worldwide became sick with TB. In the United States, there are up to 13 million people living with latent TB infection (LTBI) and 8,920 new cases were reported in 2019.
Tuberculosis can remain inactive in the body, a condition known as latent tuberculosis infection (LTBI). People with LTBI have no symptoms, don't feel sick, and cannot spread TB bacteria to others. Many people with LTBI will never develop Tuberculosis (TB) disease. However, about 5% to 10% of people, especially those who have a weakened immune system, the bacteria may become active, multiply, and cause TB disease. With TB disease the person becomes very sick, contagious, and must be isolated to prevent the spread of TB to others.
Symptoms of active TB disease include: