Coughs spread virus or bacteria by respiratory "droplets". The contagious period varies for individual diseases. For example, young children shed or spread H1N1 longer from their noses than do adults (avg. one day before being sick to up to one week there after). However, something like tuberculosis can live and be spread for a very long time. It is always best to cover your coughs and sneezes with your sleeve and wash your hands.
Wayne Yankus, MD, FAAP
expert panelist: pediatrics