It is not easy to become infected with tuberculosis. Usually a person has to be close to someone with TB disease for a long period of time. TB is usually spread between family members, close friends, and people who work or live together. TB is spread most easily in closed spaces over a long period of time. However, transmission in an airplane, although rare, has been documented.

Even if someone becomes infected with tuberculosis, that does not mean they will get TB disease. Most people who become infected do not develop TB disease because their body's defenses protect them. Most active cases of TB disease result from activating old infection in people with impaired immune systems.

Experts believe that about 10 million Americans are infected with TB germs. Only about 10 percent of these people will develop TB disease in their lifetime. The other 90 percent will never get sick from the TB germs or be able to spread them to other people.¹

TB is an increasing and major world wide problem, especially in Africawhere the spread has been facilitated by AIDS. It is estimated that nearly 1 billion people will become newly infected, over 150 million will become sick, and 36 million will die worldwide between now and 2020 -- if control is not further strengthened. Each year there are more than 8.8 million cases and close to 2 million deaths attributed to TB; 100,000 of those 2 million deaths occur among children.