Hepatitis B  

The word hepatitis refers to an “inflammation of the liver”. Hepatitis B is a potentially life-threatening liver infection which is caused by the hepatitis B virus (HBV). It is a major global health problem and the most serious type of the viral hepatitis. There are two phases of HBV infection: acute and chronic. Acute (new, short-term) hepatitis B occurs shortly after exposure to the virus. A small number of people develop a very severe, life-threatening form of acute hepatitis called fulminant hepatitis. While, chronic (ongoing, long-term) hepatitis B is an infection with HBV that lasts longer than six months and can lead to cirrhosis, or scarring of the liver, liver cancer, and liver failure. An acute hepatitis B infection can progress to chronic hepatitis B. Once the infection becomes chronic, it may never go away completely.

Not everyone who is infected with hepatitis B will develop chronic hepatitis B. In fact, most healthy adults (90%) who are infected will recover and develop protective antibodies against future infection.  Unfortunately, this is not true for infants and young children. 90% of infants and up to 50% of young children infected with hepatitis B will develop chronic infections. Therefore, vaccination is essential to protect infants and young children.

Most infected people look perfectly healthy and have no symptoms of disease, yet may be highly infectious. HBV is transmitted through percutaneous or parenteral contact with infected blood, body fluids, and by sexual intercourse.

Epidemiology

400 million people worldwide are chronically infected with hepatitis B. 280 million of those are Asian/Pacific Islanders (APIs) and 130 millions are Chinese.

The world can be divided into three areas where there prevalence of chronic HBV infection is high (>8%), intermediate (2-5%), and low (<2%).

 High endemicity areas include south-east Asia and the Pacific Basin (excluding  Japan, Australia, and New Zealand), sub-Saharan Africa, the Amazon Basin, parts of the Middle East, the central Asian Republics, and some countries in eastern Europe. In these areas, about 70 to 90% of the population becomes HBV-infected before the age of 40, and 8 to 20% of the people are HBV carriers.

Low endemicity areas include North America, Western and Northern Europe, Australia, and parts of South America. The carrier rate here is less than 2%, and less than 20% of the population is infected with HBV.

The rest of the world falls into the intermediate range of HBV prevalence, with 2 to 8% of a given population being HBV carriers.

SOURCE: Mahoney, Update on Diagnosis, Management and Prevention of Hepatitis B Virus Infection, Clinical Microbiology Reviews, 1999; CDC, PATH

Hepatitis B in the United States

The table below shows the number of cases of acute hepatitis B in the United States between year 2002 and 2007.

Below is a bar chart to show the difference between the reported cases and the estimated number of cases throughout the year according to the recorded values above.

Number of reported cases are much lower compared to the estimated cases of hepatitis B in the United States but we can see a decline in both values where the estimated cases have declined much more than the reported cases.

The table below shows a more elaborate incidence of hepatitis B in the United States that starts from the year 1980 to 2007.

From this table, a graph is plotted (below) to show how the incidence have progressed or declined throughout the recorded year.

Based on the graph, the estimated acute case starts at 53,000 in 1980. Then, the value peaks in 1985 to 74, 000 which, thereafter, descends until it reaches 13, 000 by 2007. For reported acute case count starts at 19, 014 in 1980 and then peaks to 26,612 in 1985. Afterwards, the value descends until it reaches 4, 519 by 2007.

References:

http://www.hepb.org/hepb/statistics.htm

http://www.gavialliance.org/resources/hepB_burden_463_b.gif

http://www.cdc.gov/hepatitis/PDFs/disease_burden.pdf