HIV is a fast-mutating virus that has developed into many strains since scientists first identified it in the United States almost 30 years ago. There are so many strains of HIV that scientists haven't tried to count them. While there are too many strains of HIV to number, there are 2 main types: HIV-1 and HIV-2. The HIV-1 virus has 3 main subgroups.
What Is HIV?
HIV, the human immunodeficiency virus, weakens the immune system of its victims by destroying a particular kind of blood cell, T-cells or CD4 cells, which the body needs to fight diseases. You can be infected with HIV if you have unprotected sexual contact with a person who has the virus, or if you are exposed to the blood of an infected person. For example, drug users can catch the virus if they share needles for injections with an infected person.
Without treatment, HIV can eventually destroy so many cells that the infected person will develop AIDS (acquired immunodeficiency syndrome). According to the Centers for Disease Control, a person with AIDS will fight frequent infections and may develop certain cancers or other diseases.
HIV-1
HIV-1 is the most common type of HIV. Scientists believe it is responsible for the global AIDS pandemic, according to the National Institute of Allergy and Infectious Diseases.
Within HIV-1 exist 3 main groups of HIV strains. According to the international AIDS charity known as Avert, the groups are the "major" group, M; the "outlier" group, O; and the "new" group, N.
Most HIV infections are part of the major or M group. Infections from the N group are rare, and O group infections occur mostly in west-central Africa. Group M has at least 9 different subtypes.
HIV-2
HIV-2 is transmitted through bodily fluids, just as HIV-1. But few cases of HIV-2 have been reported in the United States. The virus is most prevalent in parts of Africa, especially West Africa.
HIV-2 appears to be less easily passed from person to person than HIV-1, and it generally takes longer for an infected person to develop illness from HIV-2 than it does from HIV-1.
Recombinant Strains
Sometimes 2 different subtypes of the HIV virus can combine in the cell of an infected person, creating a new hybrid form of the virus. Many of these new strains die out quickly, but some survive and manage to infect new victims. These strains of the virus are known as "circulating recombinant forms," Avert says.
Implications
Because the HIV virus changes so rapidly, it has created many different strains and will likely continue to create new ones. This complicates efforts to develop a vaccine for AIDS, because a vaccine to produce immunity to one strain may not protect against a different strain. Also, more virulent strains of the virus could develop as it mutates.
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