On average, about how long does it take before an adult infected with HIV develops AIDS (in the absence of any drug treatment for the disease)?

The time lag between the infection and the appearance of the first symptoms of AIDS is between 5-10 years. This is incubation period. After infection, the virus enters the macrophages and replicates using its enzyme reverse transcriptase to produce viral DNA from its RNA. The viral DNA enters and incorporates into the host cells and directs the production of viral particles. Simultaneously, the viral particles attack the Helper T cells and lead to the impairing of the immune system. Therefore, a person suffering from AIDS could die of the slightest cold or infection.