Some people who contract HIV experience very strong symptoms, but others experience none at all. Those who do have symptoms generally experience symptoms similar to the common cold or flu: fever, fatigue, and, often, rash. Other common symptoms can include headache, swollen lymph nodes, and sore throat. These symptoms can occur within days or weeks of the initial exposure to the virus during a period called primary or acute HIV infection. Many infections that are not HIV can cause similar symptoms, including mononucleosis, viral hepatitis, other sexual transmitted infections, and viral hepatitis. Stress and anxiety can also produce similar symptoms in some people, even though they do not have HIV.
Because of the nonspecific symptoms associated with primary or acute HIV infection, symptoms are not a reliable way to diagnose HIV infection. Testing for HIV antibodies is the only way to know whether you have been infected; however, the HIV antibody test only works after the infected person's immune system develops antibodies to HIV. During the "window period" between the initial infection and the period in which antibodies are detectable (which can be from 2 weeks to 6 months, but is usually around 3 months), standard HIV antibody testing may be negative, even though a person is infected--it is too early for the antibody test to be positive. However, HIV can be diagnosed during this window period with a test that looks for the HIV virus itself, and not the body's response to it.
If you are concerned that you may have recently acquired HIV and have symptoms described above, see a health care provider, who can evaluate you for HIV and other possible causes of your symptoms. If early HIV infection is suspected, your provider can test directly for the virus, using a test called "PCR" or a "4th generation" HIV test that looks for the antibody and the virus at the same time), as well as doing the standard antibody test to determine whether HIV is present in the blood.
Once the primary or acute infection is over, most people do not experience any visible symptoms for another 8-10 years. Even though someone may not have active symptoms, they still have the infection and are infectious to others. Left untreated, the immune system becomes increasingly weaker and the disease progresses to AIDS. The next symptoms experienced by individuals infected with the virus are often associated with the "opportunistic infections" that target individuals with AIDS such as pneumonia, fungal infections, and HIV-specific cancers such as Kaposi sarcoma.