Many viruses and bacteria that cause disease have different strains or genetic varieties. Right now, we are in flu season. We get flu vaccinations each year because the main strain responsible for the flu changes every year and we must develop a new vaccine. The Human papilloma virus which causes genital warts, cervical and anal cancers, and head and neck cancers has over 100 strains referred to as genotypes. Most of these strains are harmless to people, but other specific genotypes are able to cause the diseases I listed.
The Hepatitis C virus (HCV) has six major strains, also referred to as genotypes. One of the most striking differences between these genotypes is their response to treatment. For example, when we used a drug called interferon to treat hepatitis C, patients with genotype 4 could expect to get cured by treatment whereas patients with genotype 1a or 1b were far less likely to experience such a benefit. Fortunately, we now have easy to take medicines that can cure all genotypes of HCV in most cases with just a couple months of treatment (more on this topic in the future).
So what about HIV? There is a lot of variation in HIV strains. First of all, you should understand that there are two major types of HIV: HIV-1 and HIV-2. For the most part, whenever you hear HIV, it is referring to HIV-1. It is by far the major virus that infects people all over the world. HIV-2 is only found in parts of West Africa.
HIV-2 is a deadly virus just as HIV-1 but it causes disease slower than HIV-1. It is also spread sexually, through birth and coming into contact with infected blood. It is possible for a person to be infected by both HIV-1 and HIV-2 but
