Hepatitis A is a vaccine-preventable infectious disease that can damage the liver. Infected people shed the virus in their stool in high concentrations from two to three weeks before to one week after onset of clinical illness, and thereby spread the virus during this time. They often carry it on poorly washed hands. It spreads to others when they swallow invisible amounts of the virus through food, drink, sexual activity or after touching contaminated objects. While proper hand washing can prevent spread of infection, vaccination provides long-term protection against the virus.