How does influenza A (H1N1-2009) spread from humans to humans?
Influenza A (H1N1-2009) spreads from human to human in the same way as seasonal flu. Flu can be spread when an infected person coughs, sneezes, or speaks. The flu viruses are transmitted into the air through droplets and other people breathe in the viruses. When these viruses enter the nose, throat, or lungs of a person, they begin to multiply, causing symptoms of the flu. The viruses can also be spread indirectly when a person touches a surface with flu viruses on it (for example, a door knob) and then touches his or her nose or mouth. Transmission can also occur when an infected person shares food with others during mealtime without a serving spoon.
