The World Health Organization says hepatitis A is often found in Africa, Asia and Central and South America. People who have had hepatitis A cannot get it again. There is a vaccine to prevent hepatitis A. America's Centers for Disease Control says the vaccine is the best way to protect against the disease.
The World Health Organization says as many as two billion people are infected with the hepatitis B virus. More than three hundred fifty million of those infected have lifelong infections. W.H.O. officials say an estimated six hundred thousand people die each year as a result of hepatitis B.
The virus is in the same group as the herpes and smallpox viruses. Hepatitis B vaccines have been given since the nineteen eighties. The W.H.O. says the vaccine is ninety five percent effective in preventing the development of infection in both children and adults.
Hepatitis B spreads when blood from an infected person enters the body of another person. An infected mother can infect her baby. The virus can also spread through sexual activity, and if people share injection devices.
Blood products from an infected person can spread hepatitis B. People also can get infected if they share personal-care products that might have blood on them. Examples include toothbrushes and hair-cutting instruments.
Worldwide, most hepatitis B infections are found in children. Young children are the ones most likely to develop a lifelong, or chronic, infection. The risk of such an infection is small for children older than four years.
About ninety percent of babies infected with hepatitis B during the first year develop chronic infections. Such persons are at high risk of death from liver disease or liver cancer. The hepatitis B vaccine is considered to be the first medicine that can protect people against liver cancer.