Flu is the short term for influenza. It is an illness caused by a respiratory virus. The flu can spread rapidly through communities, as the virus is passed person to person.
When someone with the flu coughs or sneezes, the influenza virus gets into the air, and people nearby, including children, can inhale it through the nose or mouth.
The virus also can be spread when a child touches a contaminated hard surface, such as a door handle, and then places his hand or fingers in his nose or mouth or rubs his eye.