In its early stages, HIV infection often causes transient flu-like symptoms, such as fever, sore throat, rash, nausea and vomiting, diarrhea, fatigue, swollen lymph nodes, muscle aches, headaches, and joint pain. Doctors call this acute HIV infection.
The symptoms of acute HIV can be mild. So, the person or doctor may attribute the symptoms to a routine cold or flu. In a small number of cases, this early stage of infection may progress to meningitis (inflammation of membranes covering the brain) or severe flulike symptoms that require hospitalization.
Without treatment, the number of CD4 cells almost always declines. During this time, the person may begin to develop swollen lymph nodes and skin problems, such as varicella-zoster (shingles), seborrheic dermatitis (dandruff), new or worsening psoriasis, and minor infections. Ulcers can develop around the mouth and herpes outbreaks (oral or genital) may become more frequent.
Over the next few years, as more CD4 cells continue to die, skin problems and mouth ulcers develop more often. Many people develop diarrhea, fever, unexplained weight loss, joint and muscle pain, and fatigue. Old tuberculosis infections may reactivate even before AIDS develops. (Tuberculosis is one of the most common HIV/AIDS-related infections in the developing world.)
Finally, with further decreases in the levels of CD4 cells, the person develops AIDS. According to the CDC, for an HIV-infected person, some signs that AIDS has developed (known as AIDS-defining conditions) are:
The CD4 cell count has decreased to fewer than 200 cells per cubic milliliter of blood.
An opportunistic infection has developed, indicating that the immune system is severely weakened. These types of infections include specific causes of pneumonia, diarrhea, eye infections and meningitis. Some of the causes of these opportunistic infections include Cryptococcus, reactivation of cytomegalovirus, reactivation of toxoplasma in the brain, wide-spread infection with Mycobacterium avium complex and Pneumocystis jiroveci (formerly called Pneumocystis carinii) in the lungs.
A type of cancer has developed that shows that the immune system is severely weakened. For those who are infected with HIV, these cancers can include advanced cervical cancer, Kaposi's sarcoma (a cancer causing round, reddish spots in the skin and mouth), certain types of non-Hodgkin's lymphoma and brain lymphoma.
An AIDS-related brain illness has developed, including HIV encephalopathy (AIDS dementia) or progressive multifocal leukoencephalopathy (PML) that is caused by the JC virus.
There is severe body wasting (HIV wasting syndrome).
There is an AIDS-related lung illness, such as pulmonary lymphoid hyperplasia or lymphoid interstitial pneumonia (usually seen only in children).