It is much easier to talk of the Hepatitis C virus as if it is a single organism but in fact it is a range of viruses, similar enough to be called Hepatitis C virus, yet different enough to be classified into subgroups.
Viruses are microscopic and no person could ever see them with the naked eye. Indeed, HCV is so small that there’s been no confirmed actual sighting of it using any type of microscope yet developed.
Consequently, a better way to understand the terms HCV ‘genotypes’ and ‘subtypes’ is to compare them to things that we can more readily relate to.
The group of birds we call ‘raptors’ (birds of prey) have evolved into different main types. Imagining raptors as being Hepatitis C viruses, you could take one major raptor type, such as eagles, and imagine these as being one of HCV’s main types (genotypes).
But eagles as a group are made up of different sub types such as the American Bald Eagle and Australia’s Wedge Tailed Eagle and Sea Eagle. You could imagine each of these as being one of the HCV subtypes that make up an HCV genotype.
Within each of above particular types of eagles, there are further differences. All Wedge Tailed Eagles, for example, differ from each other in regard to wing span, weight, color, beak size, etc. Similarly, within a Hepatitis C sub-type, individual viruses differ from each other ever so slightly. Such viral differences are not significant enough to form another sub-type but instead form what’s known as quasi-species. It is believed that within an HCV sub-type, several million quasispecies may exist. Scientists predict that people who have Hepatitis C, have billions of actual viruses circulating within their body. Although there may be one or two predominant sub-types, the infection as a whole is not a single entity and is composed of many different quasispecies.
Page 1 2
Genotypes and Genetic Variation of Hepatitis C Virus by G. Maerterns & L. Stuyver, reviewed by Dr Greg Dore of the National Centre in HIV Epidemiology & Clinical Research.
From The Hep C Review; Ed 23, December 1998; Paul Harvey