The Differences Between HIV-1 and HIV-2

Two Strains of the Virus that Causes AIDS

Microscope - Clarita, MorgueFiles

Many people have seen references made to two different strains of the HIV virus, HIV-1 and HIV-2, but the similarities and differences are rarely explained. Both forms of HIV are spread through sexual contact, blood, and mother-to-child transmission. There is no known cure for either form of HIV and both will eventually progress to AIDS. The symptoms of HIV-1 and HIV-2 are exactly the same and individuals cannot know which type they have without tests performed by a physician.

These two strains of the same virus were both discovered by Dr. Montagnier and his colleagues in 1983. While HIV news sources typically use the blanket term “HIV”, they are usually referring to HIV-1, since the majority of news on research, treatment, and statistics relate only to HIV-1. HIV-2, found mainly in a small area of Africa, is much rarer than HIV-1 and has special consideration for research.

Geographic Spread of HIV-1 and HIV-2

HIV-1 is found around the world, while HIV-2 is restricted to a very small portion of West Africa. Countries where HIV-2 is common include Senegal, Nigeria, Ghana, and the Ivory Coast. Outside of West Africa, HIV-2 is extremely rare. Places where it is most common are countries with strong ties to West Africa like Portugal, Angola, and France. In the United States, only about 100 confirmed cases of HIV-2 have been reported. These cases have mostly occurred in people who have traveled to West Africa.

Spread of HIV-1 and HIV-2

HIV-2 has been found to be harder to spread to others than HIV-1, though HIV-2 becomes much more infectious in the later periods of the disease progression. HIV-2 also has a longer period between when a person becomes initially infected and when they begin showing symptoms of illness. HIV-2 is slower than HIV-1 to advance to AIDS, though researchers do not yet know why this occurs. It is possible for individuals infected with one strain of HIV to become infected with the other strain.

HIV Testing and Treatment Issues

While many HIV test only test for HIV-1, newer versions of rapid HIV tests are sensitive to both HIV-1 and HIV-2. These tests are not regularly used in areas where HIV-2 is rare. Individuals who believe they may have been exposed to HIV-2 are encouraged to discuss their testing options with a physician.

HIV treatments are not as effective for treating HIV-2 as they are for HIV-1. The development of HIV treatments has mainly been done with the intention of treating HIV-1, since it affects a larger number of people. Further research is required to develop treatment targeted for HIV-2.

It is also more difficult for physicians to monitor the progression of HIV-2 since there is currently no FDA-licensed viral load test. The viral load tests that have been developed for HIV-1 are not reliable tools for monitoring the viral load progression of HIV-2 infected individuals. New tests are being developed to better monitor the viral load of HIV-2 infected individuals