Hepatitis C is like a viral family. The types could be considered like cousins. Type 1 being cousin to the other types (2, 3, 4 etc.) The sub types could be considered like brothers/sisters. 1a being a brother of 1b, 2a being a sister of 2b etc. Some types are more resilient than others and are harder to treat and this is common throughout the sub types of that type.
Just a note for anyone visiting this post in the future:
Hepatitis C is divided into six distinct genotypes throughout the world with multiple subtypes in each genotype class. A genotype is a classification of a virus based on the genetic material in the RNA (Ribonucleic acid) strands of the virus. Generally, patients are only infected with one genotype, but each genotype is actually a mixture of closely-related viruses called quasi-species. These quasi-species have the ability to mutate very quickly and become immune to current treatments, which explains why chronic Hepatitis C is so difficult to treat.
Following is a list of the different genotypes of chronic Hepatitis C:
Genotype 1a
Genotype 1b
Genotype 2a, 2b, 2c & 2d
Genotype 3a, 3b, 3c, 3d, 3e & 3f
Genotype 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i & 4j
Genotype 5a
Genotype 6a
Genotype 1 is the most common type of Hepatitis C genotype in the United States and the most difficult to treat. For physicians, knowing the genotype of Hepatitis C is helpful in making a therapeutic recommendation. Individuals with genotypes 2 and 3 are almost three times more likely than individuals with genotype 1 to respond to therapy with alpha interferon or the combination of alpha interferon and ribavirin. Furthermore, when using combination therapy, the recommended duration of treatment depends on the genotype. For this reason, testing for Hepatitis C genotype is often clinically helpful. Once the genotype is identified, it need not be tested again as genotypes do not change during the course of infection.
Genotype 4—12 weeks on triple Tx with Sovaldi.
Genotype tells you how long you have to treat. It is used for Hepatitis C not B. Genotype 1a or 1b have to treat for 48 weeks. Genotype 2 or 3 have to treat for 24 weeks. I don't know about genotype 4.