A potentially life-threatening liver infection, Hepatitis B is caused by the Hepatitis B virus which can result in chronic infection to the point of high risk of death from cirrhosis and liver cancer.
Typically, the Hepatitis B virus can survive outside the body for at least 7 days and still cause infection if it enters the bloodstream of an unvaccinated person. On an average, the incubation period of the virus is 75 days but the range can swing from 30 to 180 days. Post infection, the virus takes 30 to 60 days to be detected and can persist and develop into chronic Hepatitis B.
In highly endemic areas, the disease usually spreads through perinatal transmission (from mother to foetus/child) or through horizontal transmission (exposure to infected blood), especially from an infected child to an uninfected child under the age of 5 and the development of chronic infection through perinatal transmission is very high.
Hepatitis B spreads through percutaneous or mucosal exposure to infected blood and various body fluids, as well as through saliva, menstrual, vaginal, and seminal fluids. Sexual transmission happens particularly when unvaccinated men have sexual contact with the same sex, heterosexual partners, multiple sex partners or sex workers. Infection in adults can lead to chronic hepatitis in less than 5% of cases. The virus also spreads through the reuse of needles and syringes or exposure to infected blood during medical, surgical or dental procedures in health-care settings or during tattooing or among serial drug abusers.
Usually there are no symptoms during the acute infection phase except for exceptions that last several weeks like yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting and abdominal pain.
A small section of patients with acute hepatitis may develop acute liver failure which can be fatal. In some cases, the virus can also cause a chronic liver infection that can develop into cirrhosis of the liver or liver cancer.
More than 90% of healthy adults who contract hepatitis B virus recover naturally from the virus within the first year.
On clinical grounds, it is hugely difficult to tell Hepatitis B from other hepatitis cases due to viral agents and, hence, laboratory confirmation of the diagnosis is essential. A series of blood tests are available to diagnose and monitor people with Hepatitis B and more importantly, to distinguish acute and chronic infections.
The laboratory diagnosis focuses on the detection of the hepatitis B surface antigen HBsAg. WHO recommends that all donated blood is tested for hepatitis B to ensure blood safety and avoid accidental transmission to people who receive blood.
- Acute HBV infection is accompanied by the presence of HBsAg and immunoglobulin M (IgM) antibody to the core antigen, HBcAg. During the initial phase of infection, patients are also seropositive for hepatitis B e antigen (HBeAg). The presence of HBeAg indicates that the blood and body fluids of the infected individual have high risk of replication of the virus.
- Chronic infection is accompanied by the persistence of HBsAg for at least 6 months (with or without concurrent HBeAg). Persistence of HBsAg is the principal marker of risk for developing of chronic liver disease and liver cancer (hepatocellular carcinoma) later in life.
There is no specific treatment for acute hepatitis B except for maintaining adequate nutritional and fluid balance lost from vomiting and diarrhoea. Chronic hepatitis B infection can be treated with potent drugs like tenofovir or entecavir and oral antiviral agents. Treatment can slow the progression of cirrhosis, reduce incidence of liver cancer and improve long term survival. Treatment only suppresses the replication of the virus and hence most patients who start treatment must continue it for life. Treatment using interferon injections may be considered as well.
The WHO recommends the hepatitis B vaccine (available since 1982) be given to all infants preferably within 24 hours after birth, to be followed by 2 or 3 doses to complete the primary series. The complete vaccine series induces protective antibody levels in more than 95% of infants, children and young adults and the protection lasts at least 20 years and sometimes lifelong.