Hepatitis B virus, one of several Hepatitis viruses, accounts for a large portion of the disease burden worldwide with upwards of 350 million chronic carriers of the disease. The virus, also known as HBV, infects the liver and causes a variety of problems, including cancer. There are three main modes of transmission: through a mixing of blood products, through sexual contact, and perinatally, from mother to fetus. 5, 19
The prevalence of HBV and its patterns of transmission vary throughout regions of the world, with about 45% of the world's population living in areas of high endimicity, defined as areas where 8% of the population has a positive test for the HBsAg (the main surface antigen of the HBV viral envelope). Additionally, another 43% of the world's population lives in areas of moderate endimicity (i.e. 2%-7% of the population is HbsAg positive). Only 12% of the world's population lives in areas of low endimicty (i.e., <2% of the population is HbsAg positive). The map below outlines these areas.
Although everyone is at risk for contracting HBV, risk is increased based on certain behaviors. These include: injection drug users, sexually active heterosexuals, men who have sex with men, infants/children in disease endemic areas, infants born to infected mothers, health care workers, hemodialysis patients, people who have had more than one sexual partner in the last 6 months, those who received blood transfusions prior to 1975, hemophiliacs, patients and workers in institutions for the developmentally disabled, inmates at long term correctional facilities, and travelers to endemic areas. www.immunize.org
| Children / infants in endemic areas | Sexually active people with more than 1 partner in last 6 months | Infants born to infected mothers |
| Injection drug users | Health care workers | Hemophiliacs |
| Inmates in long term correctional facilities | Patients and workers in institutions that serve the developmentally disabled | Hemodialysis patients |
| Travelers to endemic areas | People with low socioeconomic status | People who received blood transfusions before 1795 |
Activities that increase the chances of becoming infected with HBV include unprotected sex, injection drug use, infants born to infected mothers, contact with blood or open wounds of an infected person, human bites, sharing a household with an infected individual, sharing particular personal items including toothbrushes, razors, and washcloths, using unsterilized needles (during immunization of multiple people or during body piercing), pre-chewing food for babies. www.hepnet.com , www.immunize.org
Infection with HBV can be either acute or chronic. For acute infections, the incubation period of the virus is anywhere from 6 weeks to 6 months, and only 33 to 50% of older children and adults are symptomatic. An infection is classified as chronic when the individual has HBsAg present in his or her serum for more than 6 months. Chronic carriers are at higher risk for developing cirrhosis of the liver (chronic liver disease) or liver cancer (hepatocellular carcinoma).Look at our Pathology and Treatment Page to learn more about the consequences of infection.
Interestingly, the probability of becoming a chronic carrier of HBV is inversely related to a person's age when infected. Therefore the younger one is at time of infection, the greater the likelihood of becoming a chronic carrier of HBV and thus developing severe liver problems and transmitting the infection to others. 5
In the United States, an area of relatively low endimicity, there are between 140,000 and 320,000 infections/yr, of which only 70,000-160,000 are symptomatic infections. Of these symptomatic infections, there are 8,400-19,000 hospitalizations/yr and only 140-320 (0.2%) deaths. Of all of the infections yearly, about 8,000 to 32,000 (6%-10%) cases develop into chronic viral carriers and there are 5,000-6,000 deaths per year as a result of the complications that chronic HBV infection causes. Overall, there are an estimated 1-1.25 million people infected in the United States. www.cdc.gov , www.who.int
| Unprotected sex | Sharing of personal items |
| Injection drug use | Pre-chewing food for infants |
| Contact with human blood | Sharing food or chewing gum |
| Human bites | Being born to an infected mother |
| Sharing household with infected person | Using unsterilized needles for immunization, body piercing, etc. |
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