Tuberculosis (TB) is an airborne bacterial infection caused by the bacterium (germ) called Mycobacterium tuberculosis that primarily affects the lungs, although other organs and tissues may be involved.
Key Points
- While contagious, TB is not easily spread from person to person.
- An estimated 13 million people in the U.S. live with inactive TB.
- Without treatment, 1 in 10 people with inactive TB will get sick with active TB disease.
- TB can almost always be treated and cured when medicine is taken as directed.
How TB Affects Your Body
When an individual breathes in TB germs, the germs can settle in the lungs and begin to grow. The germs can also move through the blood to other parts of the body, such as the kidney, spine, and brain.
TB bacteria can live in the body without making you sick, which is called inactive TB (or latent TB infection). When TB germs are multiplying in your body this is called active TB disease.
Someone with inactive TB:
- Has a small amount of alive but inactive TB germs in their body
- Does not feel sick or have symptoms
- Cannot spread TB germs to others
- Needs treatment to prevent active TB disease
Someone with active TB disease:
- Has a large amount of active TB germs in their body
- Feels sick and has symptoms
- Can spread TB germs to others
- Without treatment active TB disease can be fatal
How TB is Spread
TB germs are spread when a person with active TB disease of the lungs or throat coughs, speaks, or sings. These germs can stay in the air for several hours depending on the environment. TB germs are more likely to spread in indoor areas and places with poor air circulation rather than in outdoor areas.
TB germs are not spread through:
- Shaking hands
- Sharing food or drink
- Touching surfaces
- Kissing
Risk Factors for TB
Anyone can get TB, but some people are higher risk than others. The chances of getting infected by the TB germ are highest for people that are in close contact with others who are infected. This includes:
- People who recently spent time with someone who has active TB disease.
- People who were born in or frequently travel to countries where TB is common, including some countries in Asia, Africa and Latin America.
- People who live or used to live in groups settings where TB is more common, such as homeless shelters, prisons or jails.
- People who work or reside in facilities where TB is more likely to spread, such as hospitals, homeless shelters, correctional facilities, and nursing homes.
- People who have a weaker immune system because of certain medications or health conditions such as diabetes, cancer and HIV.
Some people with weakened immune systems are at very high risk for developing active TB disease once infected with TB germs. It’s important that these individuals receive treatment for inactive TB to prevent the development of active TB disease.
People at the highest risk for developing active TB disease are those with a weak immune system, including:
- Babies and young children
- People with chronic conditions such as diabetes or kidney disease
- People with HIV infection
- Organ transplant recipients
- Cancer patients undergoing chemotherapy
- People receiving certain treatments for autoimmune disorders such as rheumatoid arthritis or Crohn's disease
Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.
Page last updated: January 30, 2025
