Genetic mutations in HIV are well known and are very likely, considering the presence of two RNA molecules per virus. Either or both RNA molecules can mutate. These mutations potentially lead to drug resistance or encourage the virus to evade the body's immune response.
Mutations have resulted in groups M, N, O, and P. Most HIV-1 infections are caused by Group M viruses. Group M can further be divided into subtypes that are also referred to as clades and even sub-subtypes. Groups N, O, and P are uncommon.
The image on the right illustrates the classifications of the major HIV types, groups, and subtypes identified to date.
