Not everyone infected with TB bacteria becomes sick. As a result, two TB-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

• Don’t 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 individuals, the TB bacteria remain inactive for a lifetime without causing disease. But in others—especially those with weakened immune systems—the bacteria may become active, multiply, and cause TB disease.

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 and may 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 the immune system can fight the bacteria. Others may get sick years later when their immune system becomes weak due to other reasons. For individuals with weakened immune systems—particularly those with HIV infection—the risk of developing TB disease is much higher.

The Difference between Latent TB Infection (LTBI) and TB Disease

Symptoms depend on where in the body the TB bacteria are growing—most commonly in the lungs (pulmonary TB). TB disease in the lungs may cause symptoms such as:

• A bad cough that lasts 3 weeks or longer

• Chest pain

• Coughing up blood or sputum (phlegm from deep inside the lungs)

Other symptoms of TB disease may include:

• Weakness or fatigue

• Weight loss

• Loss of appetite

• Chills

• Fever

• Sweating at night

People with latent TB infection do not feel sick, have no symptoms, and cannot spread TB to others.

Some people develop TB disease soon after infection (within weeks), while others may get sick years later when their immune systems weaken. Overall, about 5–10% of infected persons who do not receive treatment for latent TB infection will develop TB disease at some time in their lives. For persons with weakened immune systems—especially those with HIV—the risk is much higher.

Persons at high risk for developing TB disease include:

Persons Recently Infected with TB Bacteria

• Close contacts of a person with infectious TB disease

• People who have immigrated from areas with high TB rates

• Children under 5 years old with a positive TB test

• Groups with high TB transmission—e.g., homeless individuals, injection drug users, persons with HIV

• People who work or reside with high-risk groups in hospitals, shelters, correctional facilities, nursing homes, or residential homes for individuals with HIV

Persons with Medical Conditions that Weaken the Immune System
Examples include:

• Babies and young children

• HIV infection

• Substance abuse

• Silicosis

• Diabetes mellitus

• Severe kidney disease

• Low body weight

• Organ transplants

• Head and neck cancer

• Medical treatments such as corticosteroids or organ transplant therapies

• Specialized treatment for rheumatoid arthritis or Crohn’s disease

What to Do If You Have Been Exposed to TB
You may have been exposed to TB bacteria if you spent time near someone with TB disease. TB bacteria are put into the air when someone with active TB of the lungs or throat coughs, sneezes, speaks, or sings. You cannot get TB from:

• Clothes

• Drinking glass

• Eating utensils

• Handshake

• Toilet

• Other surfaces

If you think you’ve been exposed to someone with TB disease, contact your doctor or local health department about getting a TB skin test or TB blood test. Be sure to tell the healthcare provider when you spent time with the person who has TB disease.

A person exposed to TB cannot spread the bacteria right away. Only people with active TB disease can spread TB. After inhaling TB bacteria, it must infect you and multiply in your body to cause TB disease—only then can you possibly spread the bacteria to others.

People with TB disease are most likely to spread it to those they spend time with daily—family, friends, coworkers, or schoolmates. Some develop TB disease soon after infection; others may get sick years later, especially when immunity weakens. Many people with TB infection never develop TB disease.

Preventing Latent TB Infection from Progressing to TB Disease
Many people with latent TB infection never develop TB disease. However, individuals at higher risk—including those with HIV infection, recent TB infection (within 2 years), children, injection drug users, people with diseases that weaken the immune system, the elderly, or those with improper past treatment—should take medicine to avoid developing TB disease. Several treatment options exist. Your healthcare provider will help determine the best one. Treatments for latent TB are generally easier than for TB disease.

A person with TB disease has a large number of TB bacteria in their body; several drugs are needed for treatment.

Preventing Exposure to TB Disease While Traveling Abroad
In many countries, TB is more common than in the United States. Travelers should avoid close or prolonged contact with known TB patients in crowded or enclosed environments (e.g., clinics, hospitals, prisons, or homeless shelters).

While multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB are occurring globally, they remain rare. HIV-infected travelers face the greatest risk if exposed to MDR or XDR TB.

Air travel itself carries a relatively low risk of TB infection. Travelers working in healthcare settings with potential TB exposure should consult infection control or occupational health experts for administrative and environmental preventive measures. Using personal respiratory protective devices may be necessary once those procedures are in place.

Travelers expecting prolonged exposure to TB (e.g., in shelters or clinics abroad) should have a TB skin test or blood test before leaving the U.S. If the test is negative, repeat it 8 to 10 weeks after return. Annual testing may also be recommended for those anticipating repeated or prolonged exposure. Since HIV-positive individuals often have decreased test responsiveness, they should inform their physicians of their HIV status.