The United Nations agency warns most with the disease do not know they have it and can unknowingly transmit it to others.
Hepatitis can become deadly at any time.
July 26 marks the first "UN World Hepatitis Day."
Experts say, even though it is a chronic disease, across the whole world there is very little awareness of its extent.
Hepatitis is largely spread by contaminated water and food, blood, and other body fluids.