The hepatitis B virus (HBV) is a serious problem, as it is estimated that there are about 350 million people infected worldwide. HBV is not cytopathic and the response to it depends on the relationship between viral replication and the immune status of the patient. In natural history there are two main transmission mechanisms. The first is vertical transmission, from mother to newborn babies. In this case, patients may have an immune phase with normal ALT levels and high viral load for a long time. The second is the transmission from person to person, which occurs in adolescents and adults and is characterized by a phase of immune response with increased ALT levels and lower viral load. The immune phase in these patients is either too short or missing. During periods of activity, progression to advanced fibrosis may be important. The possibility of HBsAg becoming negative during the inactive carrier phase of the virus is naturally rare and something more common after treatment, less than 5% in the long term. Finally, morbidity is important in the evolving forms, as 5 years after the diagnosis, the incidence of developing liver cirrhosis (LC) ranges from 8% to 20%. The possibility of ending in a hepatocellular carcinoma (HCC) is 2% to 5% per year in cirrhotic patients. In contrast, in those immune and in inactive carriers the possibilities of developing HCC is rare.
Efforts to improve prevention are essential to achieve eradication of the disease. In contrast, the increasingly effective treatment will decrease morbidity and mortality of patients with HBV infection. The amount of advances in the last decade have changed the diagnostic and therapeutic approach completely. In the diagnosis we have gone from the study of serological markers to the detection of HBV DNA by CRP in real time, and using this method the lower detection limit is 5-10 IU/ml and the upper 8-9 log10 IU/ml Advances in treatment are also very important, for the moment 6 medicines have been approved: lamivudine, adefovir, telbivudine, entecavir, tenofovir and pegylated interferon (Peg-IFN). The last three are the most active ones and are considered first-line medicines under the European 1 and U.S. 2 guides.