Human immunodeficiency virus (HIV) is a retrovirus, or a virus that attacks RNA instead of DNA in human cells, eventually leading to acquired immunodeficiency syndrome (AIDS). HIV by definition attacks the body's immune system defenses so that people with HIV are more susceptible to developing other diseases and infections. AIDS is then diagnosed when certain types of life-threatening illnesses (AIDS-defining illnesses) occur or when the body's immune cell count becomes so low that no defenses remain.
Viral and Fungal Infections
The diseases that infect people with HIV are called opportunistic infections, because they usually do not occur in people who have working immune systems. Some common examples that accompany HIV include frequent thrush yeast infections, especially on the skin and in the mouth; shingles, a herpesvirus infection; and CMV retinitis, an eye infection that may cause vision loss.
Lung Diseases
Viral, fungal and bacterial infections also cause many types of lung diseases in people with HIV. Tuberculosis and Pneumocystis jiroveci pneumonia (PCP) are two examples of lung diseases that are rare in healthy people who live in developed countries but are AIDS-defining illnesses in people with HIV. Even types of pneumonia that affect healthy individuals are more likely to occur and to repeat in people with HIV.
Cancers
Cervical cancer and lymphomas, which are cancers that begin in immune cells and spread throughout the body, may occur in people with HIV. Kaposi's sarcoma (KS), caused by a type of herpesvirus, is a cancer that occurs frequently in people with HIV rather than in healthy people. KS occurs mainly on the skin and can cover extensive skin sections. The disease may also spread to bones or may lead to infection at the skin lesions.
