term applied to viral infection of the liver, causing jaundice. Hepatitis A is usually food-borne with an incubation period of one month with recovery the rule. Hepatitis B is more severe and is usually transmitted by infected blood or needles or instruments contaminated by blood. It is now recognized to be sexually transmitted also. The incubation period is 3-6 months with a mortality rate of 5-20%. The virus may remain in the blood in the so-called 'carrier state'.