Virus infections in patients with AIDS.

Virus infections are common in patients with acquired immune deficiency syndrome (AIDS). Viruses can have two distinct relationships with human immunodeficiency virus (HIV); they can be opportunists if the second virus takes advantage of decreased immune function in the host or they can act as co-factors to accelerate the rate at which AIDS develops. Viruses acting as opportunists may cause no symptoms or may be life-threatening. Several, including herpes simplex, varicella zoster, cytomegalovirus and Epstein-Barr virus, can be treated with antiviral agents. Before concluding that a virus can act as a co-factor for HIV, several other possible relationships must be excluded including opportunism, co-parameters of lifestyle and prognostic markers. Studies in vitro may suggest which viruses are potential co-factors but clear evidence can come only from carefully defined cohorts of patients. Recent evidence showing that cytomegalovirus can meet these criteria is presented.