What is Tuberculosis?

Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain. Not everyone infected with TB bacteria becomes sick. As a result, two TB-related conditions exist: latent TB infection (LTBI) and TB disease. If not treated properly, TB disease can be fatal.

How is TB spread?

TB bacteria is spread through the air from one person to another. When a person with TB disease of the lungs or throat coughs, speaks, or sings, TB bacteria can get into the air. People nearby may breathe in these bacteria and become infected.

TB is NOT spread by:

• Shaking someone's hand
• Sharing food or drink
• Touching bed linens or toilet seats
• Sharing toothbrushes
• Kissing

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When a person breathes in TB bacteria, the bacteria can settle in the lungs and begin to grow. From there, they can move through the blood to other parts of the body, such as the kidney, spine, and brain.

TB disease in the lungs or throat can be infectious. This means that the bacteria can spread to other people. TB in other parts of the body, such as the kidney or spine, is usually not infectious.

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.

TB disease vs. Latent TB infection

Not everyone infected with TB becomes sick and as a result, two related conditions exist: latent TB infection and TB disease

Latent TB Infection

TB bacteria can live in the body without making you sick. This is called latent TB infection. In most people who breathe in TB bacteria and become infected, the body is able to fight the bacteria to stop them from growing. People with latent TB infection: 

• Have no symptoms
• Do not feel sick
• Can’t spread TB bacteria to others
• Usually have a positive TB skin test reaction or positive TB blood test
• May develop TB disease if they do not receive treatment for latent TB infection

Many people who have latent TB infection never develop TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. But in other people, especially people who have a weak immune system, the bacteria become active, multiply, and cause TB disease.

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TB Disease

TB bacteria become active if the immune system can’t stop them from growing. When TB bacteria are active (multiplying in your body), this is called TB disease. People with TB disease are sick. They may also be able to spread the bacteria to people they spend time with every day.

Many people who have latent TB infection never develop TB disease. Some people develop TB disease soon after becoming infected (within weeks) before their immune system can fight the TB bacteria. Other people may get sick years later when their immune system becomes weak for another reason.

For people whose immune systems are weak, especially those with HIV infection, the risk of developing TB disease is much higher than for people with normal immune systems.

A person with TB disease may or may not have symptoms. Pulmonary or laryngeal TB Symptoms may include:

• A bad cough lasting 3 weeks or longer 
• Pain in the chest
• Coughing up blood or sputum (phlegm)
• Hoarseness

Other systemic symptoms of disease are: 

• Weakness or fatigue
• Weight loss 
• No appetite 
• Chills 
• Fever
• Sweating at night