Molecular Investigation of HIV Transmission

In 1990, the U.S. Centers for Disease Control (CDC) and the Florida Department of Health and Rehabilitative Services announced their provisional finding that a Florida dentist with the acquired immunodeficiency syndrome (AIDS) had infected one of his patients in the course of dental surgery [1]. Not long after that, the dentist, David J. Acer, and later the patient, Kimberly Bergalis, died of complications of AIDS. By 1992, the CDC had completed the fieldwork and viral characterization, and the HIV Sequence Database and Analysis Unit at Los Alamos National Laboratory had completed the HIV genetic sequence analyses involved in the investigation of the case, which by this time included four additional infections that appeared to have originated from the dentist [2, 3]. Another dental patient with HIV strains matching those of Acer and the five patients was subsequently discovered. In 1994, an independent analysis of the dentist's and the six patients' viral sequences corroborated the CDC's original conclusion [4]. Nevertheless, questions persist [5], particularly about how the infections occurred and whether new cases of this kind are likely to be encountered.

These questions, for which no satisfactory answers are currently available, are understandable in light of several facts. First, apart from the Acer case, no HIV transmission from a health care worker to a patient in the United States has been documented. Furthermore, the rate of HIV infection of health care workers in health care settings in the U.S. remains relatively low: Fewer than 50 occupational transmissions had been documented as of December 1993 (there are at least twice as many possible transmissions under investigation), and most of these resulted from percutaneous exposures [6]. In addition, 22 000 patients are known to have been treated by HIV-infected dentists and surgeons and are known not to have …