Tuberculosis (TB) is a disease caused by bacteria that spread via the air from person to person. TB most commonly affects the lungs, but it can also affect other regions of the body such as the brain, kidneys, or spine. If a person with tuberculosis does not receive treatment, they may die. However, this is more likely if they have another serious illness along with TB or if they are immune compromised due to medications for another condition or HIV/AIDS. People who are infected with TB but do not show symptoms may be spreading the disease. This is called latent TB infection or LTBI. The only way to know if someone has LTBI is through testing. Some countries require people to take medication after exposure to TB in order to prevent them from developing active TB. These treatments are different for each person and usually include isoniazid for six months or longer depending on how exposed they were to determine whether they need to be treated further. TB is treatable. With proper treatment any patient with TB can be cured. Patients cannot be cured if they don't take their medications correctly or if they develop drug-resistant TB. Resistant TB is when the antibiotics used to treat the infection no longer work. This can happen if a patient fails to complete their course of therapy or if they are prescribed an incorrect dose of drugs. Resistance is also seen if a patient receives multiple prescriptions for various types of antibiotics.