Epidemiology: incidence and prevalence:
About 5% of the world’s population has chronic hepatitis B virus (HBV)
infection, and nearly 25% of carriers develop chronic hepatitis, cirrhosis, and
hepatocellular carcinoma (HCC). The prevalence of chronic HBV infection in human
immunodeficiency virus (HIV)-infected individuals is 5%-15%; HIV/HBV coinfected
individuals have a higher level of HBV replication, with higher rates of
chronicity, reactivation, occult infection, and HCC than individuals with HBV
only. The prevalence of HBV genotype A is significantly higher among men who
have sex with men (MSM), compared with the rest of the population.
Molecular mechanisms of infection, pathology, and
symptomatology: HBV replication begins with entry into the
hepatocyte. Sodium taurocholate cotransporting polypeptide was identified in
2012 as the entry receptor of HBV. Although chronic hepatitis B develops slowly,
HIV/HBV coinfected individuals show more rapid progression to cirrhosis and HCC.
Transmission and protection: The most common sources
of HBV infection are body fluids. Hepatitis B (HB) vaccination is recommended
for all children and adolescents, and all unvaccinated adults at risk for HBV
infection (sexually active individuals such as MSM, individuals with
occupational risk, and immunosuppressed individuals). Although HB vaccination
can prevent clinical infections (hepatitis), it cannot prevent 100% of
subclinical infections. Treatment and curability:
The goal of treatment is reducing the risk of complications
(cirrhosis and HCC). Pegylated interferon alfa and nucleos(t)ide analogues (NAs)
are the current treatments for chronic HBV infection. NAs have improved the
outcomes of patients with cirrhosis and HCC, and decreased the incidence of
acute liver failure.