What is HIV-2?In biology, a strain is a variety of a specific organism. Similarities exist between strains but the small differences between them is what makes each a separate strain from the other. HIV-2 is a less common strain of HIV than is the more common HIV-1 strain. As much as they are alike they have subtle differences.
How are HIV-1 and HIV-2 Similar?Being the same virus, there are many similarities between HIV-1 and HIV-2. These similarities include:
- the modes of HIV-1 and HIV-2 transmission are the same - sexual contact, sharing needles, etc.
- people infected with HIV-2 are subject to the same opportunistic infections as those people infected with HIV-1
- HIV-1 and HIV-2 are treated with the same medications however certain drug classes work better fighting HIV-1 than HIV-2
- CD4 monitoring requires the same blood test for HIV-1 and HIV-2.
How are HIV-1 and HIV-2 Different?There are many differences between HIV-1 and HIV-2. They include:
- HIV-2 seems to weaken the immune system more slowly than HIV-1
- those people with HIV-2 are less infectious early in the course of the disease compared to those people with HIV-1
- HIV-2 seems to be more infectious later in the course of disease when compared to HIV-1
- HIV-2 occurs in different parts of the world compared to HIV-1
- there is no FDA licensed viral load test for HIV-2 and the viral load test used for HIV-1 is not reliable for HIV-2
Where in the World is HIV-2 Most Common?HIV-2 is highly concentrated in West Africa countries such as Senegal, Nigeria, Ghana, and the Ivory Coast. HIV-2 also spreads to other parts of the world but predominantly to those countries having strong ties to West Africa; France, Portugal, and Angola to name three. Very few cases are actually reported outside of these area but on occasion do surface because of international travel.
Who's Most at Risk for HIV-2 Infection?HIV-2 is transmitted in the same way as HIV-1. Certain people are, however, more at risk. They include:
- people having unprotected sexual contact with partners from areas where HIV-2 is common
- those having unprotected sex with someone diagnosed with HIV-2
- people who share needles with HIV-2 positive people or with people from areas where HIV-2 is common
- people who receive blood product transfusion in countries where HIV-2 is common
- people receiving medication injections in countries where HIV-2 is common and sterile technique is not always used.
Should I Be Tested For HIV-2?HIV-2 testing is usually limited to those people who fit into one of the high risk populations discussed earlier. However, many HIV testing sites will perform an HIV-2 test as part of HIV testing if the HIV-1 ELISA and Western Blot tests are indeterminate (neither positive or negative) or positive.
If you feel you may fall into an HIV-2 risk category or you have traveled to areas where HIV-2 is prevalent (e.g. West Africa) talk with your doctor or test counselors at your local HIV testing agency.
de Cock, K. et. al:"Epidemiology and transmission of HIV-2: why there is no HIV-2 pandemic"; JAMA 270:17 pp 2083-2086, 1993.