Hepatitis B virus is transmitted between people by contact with the blood or other body fluids (i.e. semen and vaginal fluid) of an infected person. It has the same way of transmitting the virus like the human immunodeficiency virus (HIV), but HBV is 50 to 100 times more infectious. Unlike HIV, HBV can survive outside the body for at least 7 days. During that time, the virus can still cause infection if it enters the body of a person who is not infected.
Common modes of transmission in developing countries are:
- perinatal (from mother to baby at birth)
- early childhood infections (inapparent infection through close interpersonal contact with infected household contacts)
- unsafe injections practices
- blood transfusions
- sexual contact
In many developed countries (e.g. those in Western Europe and North America), patterns of transmission are different than those mentioned above. Today, the majority of infections in these countries are transmitted during young adulthood by sexual activity and injecting drug use. HBV is a major infectious occupational hazard of health workers.
HBV is not spread by contaminated food or water, and cannot be spread casually in the workplace.
The virus incubation period is 90 days on average, but can vary from about 30 to 180 days. HBV may be detected 30 to 60 days after infection and persist for widely variable periods of time.
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