Hepatitis B virus


Hepatitis B is caused by a DNA virus identified in a spherical particle (d particle) of 42 nm diameter, with an isometric capsid, a circular bicatenary DNA genome and a pericapsidic involucre of cellular origin.
Hepatitis B virus (HBV) is a very resistant pathogen: it survives at room temperature (up to six months), it endures cold (below 20C up to several years), heat (60C up to 4 hours) and UV irradiation.
It is inactivated by high temperatures (121C) and by stove and autoclave treatment.
HBV virus is highly infective, in fact it has been estimated that it is 100 times more infective than HIV virus. The virus is present in all bodily liquids and secretions (blood, saliva, sperm, vaginal secretions, urine).
The virus is mainly spread by:
- the parenteral or percutaneous route: injections, cuts, transfusions, blood products.
- the sexual route: genital mucosa lesions, oral mucosa lesions.
- the vertical route: from mother to fetus.
- the perinatal route: mixing of blood during delivery.
In the hospital environment the transmission of HBV can occur through accidental percutaneous prick with needles or sharp contaminated objects, contact with infected blood through solutions of continuity of the skin, contamination of mucous membranes.
Once the infection has been contracted, about 90% of the subjects recover completely and 5-10% become chronic carriers of the virus. Amongst the latter 20-25% develop active chronic hepatitis which may lead to cirrhosis and liver carcinoma. About 0.5-1% of the subjects develop acute fulminant hepatitis which generally leads to death.
The risk of HBV infection following one single accidental exposure is between 2 and 40% depending on the HBeAg state of the patient source of infection.




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Hepatitis B virus