Around one third of the global population, or 2 billion people, have been infected with the liver disease hepatitis which kills about a million victims annually, the World Health Organization said on Tuesday.
And although most of those carrying hepatitis do not know they have it, they can unknowingly transmit it to others and at any time in their lives it can develop to kill or disable them, the United Nations agency warned.
"This is a chronic disease across the whole world, but unfortunately there is very little awareness, even among health policy-makers, of its extent," WHO hepatitis specialist Steven Wiersma told a news conference.
The conference marked the first U.N. World Hepatitis Day, called by the world body to raise awareness of the viral disease, largely spread by contaminated water and food, blood, semen and other body fluids.
Wiersma said the disease -- which has five main viruses -- produced a "staggering toll" on health care systems around the globe and had the potential to spark epidemics, as well as being the main cause of liver cirrhosis and cancer.
Of the five viruses dubbed A, B, C, D and E, a new WHO document says, B was the most common and could be transmitted by mothers to infants at birth or in early childhood as well as through contaminated injections or injected drug use.
The E virus, transmitted through infected water or food, is a common cause of outbreaks of the disease in developing countries and is increasingly observed in developed economies, according to the WHO.
The WHO says effective vaccines had been developed to combat the A and B viruses and could also be used against D. A vaccine for hepatitis E had been developed but was not widely available, while there was none for the C virus.
Vaccination campaigns had scored considerable success in many countries, with about 180 of the WHO's 193 member states now including the B vaccine in infant immunization programs, the agency said.
But more needed to be done to prevent or control the disease. It was vital to ensure that people already infected could be tested and given quality care and treatment without delay, the WHO document declared.