There are six main hepatitis C genotypes, named 1, 2, 3, 4, 5, and 6. Hepatitis C is a bloodborne disease caused by the hepatic C virus (HCV). The virus attacks the liver, often without symptoms for many years, and can eventually cause liver infection, scarring, and ultimately failure. All hepatitis C genotypes, however, can be managed with treatment, though the exact indications may change depending on the genotype and subtype. Hepatitis C genotypes 1, 2, and 3 are the most common, and 2 and 3 have the most successful cure rates.
The hepatitis C virus is transmitted through intravenous drug use; sex; blood transfusions and organ transplants before HCV screening was required; dirty instruments for medical use, piercing, or tattooing; or in utero from mother to child. The first sixth months after infection is called the acute phase, and is the period of time when the disease is most treatable. Most people, however, do not experience any symptoms during this time and don’t catch the disease until it has developed into its chronic phase and begun to cause liver scarring. Symptoms during the acute phase mimic mild flu symptoms and chronic hepatitis C may be characterized by jaundice, nausea, decreased appetite, fatigue, joint pain, mood changes, and trouble sleeping. As the disease progresses to cirrhosis, or extensive scarring, it can cause enlargement of the veins, or varices, build-up of fluid in the abdomen, or ascites, stunted liver function, and confusion or coma.
The hepatitis C virus is a very small RNA virus, or a virus that uses RNA as its genetic material. The various genotypes share the same basic form of the virus, with RNA on the inside and an outer layer composed of proteins and enzymes, which enables the virus to hijack the cells of the liver to reproduce themselves.
The different hepatitis C genotypes have slightly different genetic makeup, however, allowing the virus to evade scientists’ attempts to develop a vaccine that will work against all of the hepatitis C genotypes and the many subtypes. While the genotype can determine the duration of treatment and the likelihood of success, it is not thought to determine the extent of liver damage. Some studies have also indicated that different genotypes may respond differently to different types of interferon treatments.
Hepatitis C genotypes 1, 2, and 3 are the most common genotypes, especially in the United States. HCV 1 has two subtypes, 1a and 1b. 1a is the most common type of hepatitis C in North and South America and 1b is the most common type in Europe and Asia. It is more difficult to treat than genotypes 2 or 3 and is usually treated with higher doses of ribavirin or interferon for a longer amount of time. Genotype 2 has three subtypes, 2a, which is common to China and Japan, 2b, which is common to the United States and Northern Europe, and 2c, which is common to Southern and Western Europe. Genotype 3 is most common in the South Pacific. Both hepatitis C genotypes 2 and 3 have shorter treatment periods, usually around six months, lower doses of ribavirin or interferon, and higher cure rates.