Acute HIV infection refers to the first stage of infection, the time immediately after a person is infected and before an antibody response to the infection develops. The second stage of infection is seroconversion, when a person develops HIV-specific antibodies. During acute HIV infection, there are high levels of virus since the antibody response has not yet developed.
Determining acute HIV infection is critical for HIV prevention efforts. Conventional HIV tests do not detect acute infection, yet it is estimated that almost half of new HIV infections may occur when a person with acute infection unknowingly transmits HIV.
There is no defined acute retroviral syndrome since there are many different symptoms associated with acute HIV infection. After an incubation period of 1 to 3 weeks, about 50% of persons with acute HIV infection develop headaches, sore throat, fever, muscle pain, anorexia, rash, and/or diarrhea. The symptoms are generally mild and may span anywhere from days to weeks.
It is easy to overlook or miss the signs of acute HIV infection. Half of persons who are acutely infected will never notice any symptoms. Also, the symptoms of acute retroviral syndrome are similar for other common illnesses such as infectious mononucleosis and influenza, which means acute HIV infection often goes undiagnosed.