Hepatitis Virus Classification
Hepatitis virus classification includes seven types of hepatitis viruses, labeled with letters from the Latin alphabet. Hepatitis A virus or HAV affects the liver, causing an acute infectious disease called hepatitis A or just infectious hepatitis. The most common way of transmission is oral, through contaminated food or contaminated drinking water. The hepatitis A virus has an incubation period varying from two to six weeks. This condition affects millions of people every year all around the world especially in developing countries and poor regions. Once a person contracted the virus the immune system produces antibodies that confer immunity for next potential infections. The HAV outbreaks are successfully prevented by vaccination. HAV has only one serotype but several genotypes are known.
Hepatitis B virus (HBV) is responsible for the disease with the same name but it can also cause cirrhosis and hepatocellular carcinoma. Patients infected with HBV have a more increased risk to develop pancreatic cancer. There are four serotypes of the HBV virus, adr, adw, ayr and ayw, and eight genotypes, named from A to H. the severity of the disease and the possibility to evolve into more complicated forms are linked to the differences between the genotypes. There is a vaccine available to prevent infection with HBV.
Hepatitis C virus (HCV) is part of the Flaviviridae family and it is a single strand RNA virus, different than HAV and HBV. Even though they have similar names since they are all responsible for liver inflammation, these viruses are quite different. HCV is classified into six genotypes, labeled from 1 to 6, and subtypes for each genotype which are named with letters. Also each subtype is formed by many quasispecies. Currently there is no vaccine available to prevent infection with HCV and the genotype plays a very important role in the determination of the treatment followed. Usually, it is treated with an interferon-based therapy.
Hepatitis D virus or Hepatitis delta virus is a RNA virus which is activated only in the presence of the HBV virus. It can only be transmitted through an infection caused by HBV (at the same time) which is called co infection, or through the infection of a person who was infected with HBV in the past, which is called super infection. In 1955, the hepatitis E virus was documented the first time, a very small virus of only approximately 30 nanometers in diameter. In 1955 this virus caused an outbreak of hepatitis E in New Delhi, India. There is a vaccine available against HEV. In the 1990s it was believed that there existed a hepatitis F virus but after several studies the actual existence of the virus could not be proven. However, the most recently observed hepatitis virus is the HGB or hepatitis G virus. It was first documented in 1996 and it is believed to be distantly related to HCV.
Hepatitis virus classification includes many types of hepatitis viruses but in fact the most common are HAV which affects approximately 10 million people worldwide and HBV infecting more than 2 billion people worldwide.