As many as 1 million individuals in the United States are infected with the human immunodeficiency virus (HIV).1 For these persons, and especially for the approximately 250 000 who have severe immunosuppression as measured by a CD4+ lymphocyte count below 0.20×109/L (200/μL) (includes persons with [T. Green, PhD, Centers for Disease Control and Prevention (CDC), unpublished results, 1994] and without2 AIDS-defining illnesses) opportunistic infections exact a heavy toll in terms of quality and length of life. Among patients with severe immunosuppression, the cumulative risk of serious opportunistic infection has been estimated to be 33% after 1 year and 58% after 2 years.3 In addition to the morbidity and mortality associated with these opportunistic infections, treatment of these illnesses costs billions of dollars annually.
The last 5 years have witnessed a gratifying surge in our knowledge of the environmental sources of opportunistic pathogens, ways to reduce
Kaplan JE, Masur H, Jaffe HW, Holmes KK. Reducing the Impact of Opportunistic Infections in Patients With HIV InfectionNew Guidelines. JAMA. 1995;274(4):347-348. doi:10.1001/jama.1995.03530040075045