A P ATIENT WITH HIV-1

HE detection of an increasing number of circulating recombinant strains of human immunodeficiency virus type 1 (HIV-1) indicates that genetic recombination can occur in cells infected with two strains of HIV-1. 1,2 Coinfection with two circulating strains of HIV-1 has been detected in a few subjects in communities where HIV-1 infection is endemic. 3 Coinfection may result from exposure to a second virus either shortly after the initial infection or during the course of established HIV-1 infection; the latter circumstance is called superinfection. Most viral infections induce lifelong immunity, but reinfection with respiratory viruses such as respiratory syncytial virus is common, most likely because immunity becomes nonprotective or fades. It is thought that HIV-1 superinfection is a rare event 1-6 and that it is prevented by previous viral exposure through a phenomenon called superinfection immunity. 5 However, HIV-1 superinfection has been induced experimentally in chimpanzees. 7 In this animal model and in superinfection induced with the simian immunodeficiency virus in macaques, the second infection produces a slower deterioration in immunity than does the initial infection, 7-9 and there is more efficient control of viremia. In this article, we report a case of HIV-1 superinfection.