Infectious diseases like influenza, pneumonia, and tuberculosis are spread through the air. Infectious agents can be spread to others through airborne droplets when an infected person coughs or sneezes. When you start coughing or sneezing, make sure you cover your mouth with a face mask or a tissue, then dispose of it properly. When you cough or sneeze and don’t have a tissue handy, cover your mouth as much as possible with the crook (or inside) of your elbow.