Contagiousness
The viral load in the blood is a good predictor of the likelihood of transmitting HIV to another. The higher the viral load value, the more viral elements there are in tissues and in circulating blood and other body fluids. Individuals with HIV are most contagious during the earliest (acute) stages of the infection. At this phase the immune response is still developing and antibody levels against the virus are often too low to be detected. Antibody testing at this stage often yields a negative result. This scenario increases the importance of HIV education and early detection and diagnosis. Widespread testing could provide significant public health benefits. There is no safe period for an individual infected with HIV. HIV can be passed to another individual even when the viral load has dropped to undetectable. The viral load test only detects the amount of virus circulating in the blood (about 2%). Approximately 98% of the HIV is actually in the body tissues such as the lymph nodes, gut-associated lymphoid tissue (GALT), spleen, brain, and other body tissues and fluids. Viral level fluctuations in these tissues parallel the levels in the blood but there is not an immediate correlation in time or rate.
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