The DiseaseHepatitis B is a disease caused by the hepatitis B virus, and can be acute or chronic. Infection with hepatitis B virus is the leading cause of chronic hepatitis worldwide and people with chronic hepatitis B infection are at increased risk for developing liver cancer (hepatocellular carcinoma). In addition, the hepatitis B virus is the leading cause of cirrhosis in the world.
In the United States, about 1.5 million people are infected with the hepatitis B virus. However, worldwide, about 400 million people have the virus, with most of these people living in Asia. Clearly, this is a significant public health and medical problem.
Acute hepatitis B is when a person exposed to the hepatitis B virus begins to develop the signs and symptoms of viral hepatitis. This period of time, called the incubation period, is an average of 90 days, but could be as short as 45 days or as long as 6 months. For most people this infection will cause mild to moderate discomfort but will go away by itself because of the body's efforts in fighting the virus. Other people could have very serious problems such as fulminant liver failure.
Chronic hepatitis B is when a person has acute infection but is unable to get rid of the infection. Whether the disease becomes chronic or completely resolves depends mostly on the age of the infected person. About 90% of infants infected at birth will progress to chronic disease. However, as a person ages, the risk of chronic infection decreases such that between 20%-50% of children and less than 10% of older children or adults will progress from acute to chronic infection.
SymptomsIn general, the symptoms of acute hepatitis B are the same for all acute viral hepatitis. Usually the first symptom is a loss of appetite (called anorexia), followed by nausea, and then perhaps, vomiting. In some people these symptoms can be serious, lasting several weeks and requiring medical care. Other symptoms are extreme tiredness, weight-loss, aches and pains of muscles and joints, headache, light sensitivity, sore throat, cough, and runny nose.
These symptoms usually appear after the incubation period, which is an average of 90 days. As explained earlier, this is the time between infection with the virus and the appearance of symptoms. This means that if a physician could diagnose you with hepatitis B at the earliest possible moment, you were actually infected weeks earlier. It simply takes a period of time for the virus to damage the liver sufficiently enough before the body responds with the symptoms associated with viral hepatitis.
Jaundice, which is the accumulation of the chemical bilirubin in the body's tissues, is another possible symptom. This appears as a yellow coloring to the skin and around the whites of the eyes. While this is the most recognizable viral hepatitis symptom, jaundice only develops in about 30% of people with hepatitis B -- the majority of people with acute hepatitis B will not have any jaundice. In fact, it is not unusual for people with acute hepatitis B to have no symptoms. These people are said to be asymptomatic and might not even be aware of their infection. Most symptoms are usually gone after 1-3 months, but many people note continued tiredness for much longer.
TransmissionThe hepatitis B virus is most easily spread by infected body fluids coming into contact with your mucous membranes or blood. Body fluids which are most often identified as infectious are blood, saliva, semen and vaginal secretions. For health care workers, many more body fluids are considered potentially infectious and precautions are required.
The most common ways that hepatitis B virus spreads is through sexual or extremely familiar contact with someone infected, sharing needles and syringes with someone infected, and the birthing process from an infected mother to the child. In fact, this last type of spread, called perinatal transmission, was so common that public health officials began recommending routine childhood hepatitis B vaccination. Some sources say that as many as one-third of Americans with chronic hepatitis B infection were infected as infants or young children.
DiagnosisDoctors diagnose hepatitis B by testing your blood for the presence of antibodies to a specific part of the hepatitis B virus. That specific part is called HBsAG, and it stands for hepatitis B surface antigen. This antigen is actually viral protein that the body will recognize as something that shouldn't be around and will start developing an immune response against it.
Another antibody that doctors measure in your blood, called IgM anti-HBc, is an even better test for establishing acute hepatitis B infection. This measures the IgM antibody created by your body's immune system to a different viral protein called core antigen.
The body's immune response against the virus is usually very effective because most people will completely get rid of the virus. Depending on how vigorous this immune response is, and the degree of infection, you might not even realize you are sick!
However, some people do not clear the virus and they develop chronic hepatitis B. Doctors diagnose this disease by measuring both HBsAg and the antibody to the core protein, called anti-HBc. People with chronic hepatitis B have both of these circulating in their blood.