Tuberculosis is usually spread when an infected person talks, coughs, spits, laughs, shouts, sings or sneezes. This sends a spray of very small droplets into the air (i.e. airborne droplet spread). Live TB bacilli (plural of bacillus) from the patient’s lungs then float in the air and may be breathed in by other people. The inhaled TB bacilli can cause an infection of the lung. Tuberculosis is usually spread from adults with untreated tuberculosis of the lungs (pulmonary tuberculosis). Therefore, a child (the contact) with tuberculosis almost always has been in close contact with an adult with pulmonary tuberculosis (the source). It is less common for a child to catch tuberculosis from another child as children usually do not cough up TB bacilli in such large numbers. Adults with untreated tuberculosis are a danger to children in the family.