What is the difference between HIV-1 and HIV-2?
HIV-1 and HIV-2 are transmitted by exchange of bodily fluids through sexual contact, needle sharing, etc. It appears that HIV-2 is less easily transmitted, and the period between initial infection and illness is longer in the case of HIV-2.
The predominant virus is HIV-1. Generally when people refer to HIV, HIV-1 is the type being referred to. HIV-2 is relatively uncommon and is concentrated in West Africa. It is rarely found elsewhere.
How many subtypes of HIV-1 are there?
The strains of HIV-1 can be classified into four groups: the “major” group M, the “outlier” group O and two new groups, N and P. These four groups may represent four separate introductions of simian immunodeficiency virus into humans.
What are the different levels of HIV classification?
Group O appears to be restricted to west-central Africa and group N, a strain discovered in 1998 in Cameroon is extremely rare. In 2009 a new strain closely relating to gorilla simian immunodeficiency virus was discovered in a Cameroonian woman. It was designated HIV-1 group P. More than 90 percent of HIV-1 infections belong to HIV-1 group M. Within group M there are known to be at least nine genetically distinct subtypes of HIV-1. These are subtypes A, B, C, D, F, G, H, J and K.
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