Tuberculosis is an infectious disease that spreads from person to person through the air. When people with pulmonary (lung) TB cough, sneeze or spit, they propel the germs that cause TB into the air. A person needs to inhale only a few of these germs to become infected. TB can infect any part of the body, but most often it attacks the lungs. An infected person does not necessarily feel ill. Without symptoms, the disease is known as silent or latent TB. In a person with pulmonary TB, the symptoms include a cough that lasts for more than two to three weeks, weight loss, fever, night sweats, loss of appetite and coughing up blood. As TB progresses, it further attacks the lungs and other organs. Untreated, the disease is often lethal. The main causes of death are heavy bleeding from the lungs and respiratory failure. Anyone can get TB, but the disease is strongly linked to poverty and malnutrition. The overwhelming majority of people with TB can be cured by administering a six-month course of drugs costing about US$ 20.