Most symptoms of human immunodeficiency virus (HIV) infection do not appear until an individual has begun to experience the immune deficiency that develops after a long-term infection. This typically happens many years after an initial infection with the virus. On average, the symptoms of immune deficiency appear eight to 10 years after viral infection, but they may not appear for even longer time periods.
Some people experience a flu-like illness at the time of initial infection with HIV. Not all people who become infected will have these symptoms, and it is unclear why some people do and others don't. The initial infection can be mild or very severe and can be accompanied by fever, swollen lymph nodes, joint and muscle aches, and sore throat. Other symptoms can include chills, night sweats, and mouth ulcers. The symptoms and signs of the initial HIV infection have also been compared to infectious mononucleosis.
Typically after years of infection with the virus, symptoms begin to appear that reflect a decreasing immune function due to a decline in the number of CD4 T cells. These symptoms can include fungal infection of the mouth (thrush) or vagina, rashes, fungal infections of the nails, fatigue, diarrhea, vomiting, leukoplakia of the tongue, and weight loss.
If there is a further decline in immune function, more serious symptoms and signs can develop, such as dementia and cognitive changes, severe weight loss, wasting syndrome, opportunistic infections, and malignant tumors. Some of the opportunistic infections that can occur are cytomegalovirus infection, cryptococcal meningitis, Cryptosporidium diarrhea, Pneumocystic jiroveci pneumonia (previously called Pneumocystic carinii pneumonia or PCP), Toxoplasma encephalitis, tuberculosis, and herpesvirus infections. Malignancies that typically arise as a result of HIV infection include Kaposi's sarcoma and non-Hodgkin's lymphoma.