Globally, TB disease kills more than any other microbial disease in the world, an estimated 2-3 million per year. Next to HIV disease, TB is considered the world’s leading global health threat. An estimated 10 to 15 million persons in the U.S. are infected with TB. Without intervention approximately 10% of those persons will develop TB disease.
TB, or tuberculosis, is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria can attack any part of your body, but they usually attack the lungs. TB is spread through the air from one person to another. The bacteria are expelled into the air when a person with TB disease of the lungs or throat coughs or sneezes. People nearby may breathe in these bacteria and become infected.
People, who become infected with TB bacteria, usually have had very close, day-to-day, contact with someone who has TB disease (e.g. a family member, friend, or close co-worker). You’re not likely to get infected from someone coughing in line at a supermarket or at a restaurant. Dishes do not spread TB, nor do drinking glasses, sheets or clothing. In most people who become infected, the body is able to fight the bacteria to stop them from growing. The bacteria become inactive, but they remain alive in the body and can become active later. This is called latent TB infection (LTBI). People with latent TB infection:
- Have no symptoms
- Don’t feel sick
- Can’t spread TB disease to others
- Usually have a positive skin test reaction
- Can develop TB disease later in life if they do not receive treatment for LTBI.
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 weak immune systems, the bacteria become active and cause TB disease. People with LTBI can take medicine so that they will never develop TB disease.
TB bacteria become active if the immune system can’t stop them from growing. The active bacteria begin to multiply in the body and cause TB disease. Some people develop TB disease soon after becoming infected, before their immune system can fight the TB bacteria. Other people may get sick later, when their immune system becomes weak for some reason. Babies and young children, people infected with HIV, persons with chronic disease(s), and the elderly, may have weaken immune systems. Other people can have weak immune systems, especially people with any of these conditions:
- Substance abuse
- Diabetes mellitus
- Cancer of the head or neck
- Leukemia or Hodgkin’s disease
- Severe kidney disease
- Low body weight
- Certain medical treatments (such as corticosteroid treatment or organ transplants)
- The Food and Drug Administration (FDA) has determined that tuberculosis (TB) disease is a potential adverse reaction from treatment with the tumor necrosis factor-alpha (TNF-α) antagonists infliximab (Remicade®), etanercept (Enbrel®), and adalimumab (Humira®). – Centers for Disease Control and Prevention. “Tuberculosis Associated with Blocking Agents Against Tumor Necrosis Factor-Alpha — California, 2002 – 2003.” MMWR August 5, 2004 / 53(30);683-686, http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5330a4.htm (4/05)