Hepatitis A (HAV) is a contagious disease, spread by contact with infected people, their fluids and waste. It causes an acute infection of the liver that generally does not require treatment and can self-resolve. Young children infected with HAV typically have a milder form of the disease compared to adults who can be at risk of acute liver failure, especially if there is underlying chronic liver disease. HAV can affect people of all ages but can be prevented with vaccination.