HIV may manifest, at first, as symptoms of the common flu or fail to produce any symptoms at all. A diagnosis, therefore, may be difficult to initially come to.
If you believe you have been exposed to HIV, it is important to get tested early. The diagnosis of HIV infection is based on laboratory detection of infection through blood, oral fluid, or urine specimen. AIDS, the advanced stage of HIV, can be diagnosed in HIV-infected persons based on laboratory evidence of immunodeficiency (lowered levels of CD4+ cells) or clinically by onset of any of a specific list of opportunistic diseases that occur namely in patients whose immune systems are impaired by the AIDS virus.