An estimated 10 to 60 percent of individuals with early HIV infection will not experience symptoms. The exact proportion is difficult to estimate since patients generally seek medical attention because of symptoms, and thus asymptomatic infections often remain undetected.

An estimated 1.1 million persons in the United States have been infected with HIV; at the end of 2003, approximately 405,926 persons were living with AIDS. The number of reported cases in 2003 was essentially the same as the number in 1999. This trend follows a period of sharp decline in reported cases after the introduction of HAART (Highly Active Antiretroviral Therapy).
The tests to detect HIV are based on detecting either an antibody (our body own immune response) or an antigen( the virus or parts of the virus itself).

The standard third generation enzyme linked immunosorbent assays (ELISAs or immunoassays) used in clinical practice and in blood banks in the United States do not detect antibodies to HIV until three to seven weeks after symptoms.

Thus, depending on the time since infection and the sensitivity of the ELISA used, patients with acute HIV infection may have both a negative ELISA test and a negative Western Blot test or a positive ELISA with a negative or indeterminate Western Blot.

HIV RNA detection (Viral Load) — Early HIV infection is characterized by markedly elevated HIV RNA levels or viral load, easily detectable with the HIV RNA (viral load) assays commonly used for monitoring of HIV disease.

Following infection with HIV, the time at which antibodies against HIV antigens can be detected in the serum depends upon the sensitivity of the serologic test as well as the person’s own immune system.