The Human Immunodeficiency Virus, or HIV, tends to mutate very easily, resulting in different strains. All strains fall under one of two types of HIV, either HIV-1 or HIV-2. Blood and body fluids are responsible for transmission in all cases, and all lead to the Acquired Immune Deficiency Syndrome, or AIDS, if left untreated. The large majority of HIV strains fall under HIV-1, as HIV-2 is relatively uncommon and is concentrated in West Africa. There are no recognized strains categorized under HIV-2.
Group O
The HIV strain known as Group O appears to be restricted to west-central Africa and the countries of Cameroon and Gabon. According to the University of South Carolina School of Medicine, the letter O stands for “outlier” or “other,” as this strain is fairly uncommon.
Group N
Discovered in the African nation of Cameroon in 1998, the Group N strain is extremely rare, according to the international AIDS charity AVERT. The USC School of Medicine notes that the “N” in this case stands for “new.”
Group P
Doctors diagnosed a woman in Cameroon with a strain closely resembling the ape version of AIDS, gorilla simian immunodeficiency virus. Known as Group P and uncovered in 2009, this strain is also quite rare and isolated.
Group M
The USC School of Medicine notes that the “M” stands for “major.” This is because unlike O, N and P, which account for fewer than 10 percent of all HIV-1 strains, more than 90 percent of HIV-1 infections belong to the Group M strain, according to AVERT. There are at least 10 different HIV-1 subtypes within the M group strain designated A to J. Type B of the Group M strain is predominant across the U.S., Latin America, the Caribbean, Europe, Japan and Australia. Evidence suggests that type B spreads most effectively via anal intercourse and intravenous drug use.
