Within weeks of infection (upto 6 months post-infection) HIV RNA and Antigen levels rise and seroconversion occurs.
Co-inciding with Seroconversion (occuring usually between 3-4 weeks), approximately 90% of people will suffer from flu-like illness which is self-limiting.
After this primary phase, infected patients go into an asymptomatic phase that can last anywhere between 2 and 10 years (these people are physically well but infectious).
The Asymptomatic phase is known as the set point - levels of HIV antigen fall to undetectable levels with HIV RNA levels also falling dramatically. The drop in detectable Antigens and RNA and the asymptomatic effect is due to a dynamic equilibrium being reached between viral replication and destruction (this can give an idea of how likely disease progression is within the next five years).
After the Asymptomatic phase, comes the prodromal phase where a variety of prodromal disorders set in e.g. persistant cadidiasis, diarrhoea, weight loss etc.
HIV can then progress to AIDS which sees the onset of a variety of different diseases/infections e.g. rare malignancies, neurological disease etc.
Infact the majority of deaths in HIV positive patients is due to secondary infections such as pneumonia and not HIV infection itself.
The ELISA/EIA/LIA and S/R format tests all detect Anti-HIV IgG indicating infection if positive.
RTPCR is used to detect the genetic material of the virus itself.
Antibody levels are detectable in the majority of the population between 3 and 4 weeks, rarely has it been discovered that someone has taken 6 months to develop detectable Antibody levels. This is the reason many health authorities recommend the 6 month test.
The "rapid" ELISA type methods have a very high (99.5%) sensitivity, that means you have 99.5% chance of detecting Antibodies in the 3-4 week (for majority of people) period. Basically you have virtually no chance of being positive if the test says your negative.
However, the high sensitivity slightly lowers the specificity of the test leading to the chance of false positive results. This means that if you do have a positive result, they use a more specific method to confirm this diagnosis.
Hope this helps
