Human immunodeficiency virus type 1 (HIV-1) transmission from infected patients to health-care workers has been well documented, but transmission from an infected health-care worker to a patient has not been reported. After identification of an acquired immunodeficiency syndrome (AIDS) patient who had no known risk factors for HIV infection but who had undergone an invasive procedure performed by a dentist with AIDS, six other patients of this dentist were found to be HIV-infected. Molecular biologic studies were conducted to complement the epidemiologic investigation. Portions of the HIV proviral envelope gene from each of the seven patients, the dentist, and 35 HIV-infected persons from the local geographic area were amplified by polymerase chain reaction and sequenced. Three separate comparative genetic analyses--genetic distance measurements, phylogenetic tree analysis, and amino acid signature pattern analysis--showed that the viruses from the dentist and five dental patients were closely related. These data, together with the epidemiologic investigation, indicated that these patients became infected with HIV while receiving care from a dentist with AIDS.

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This section looks back to some ground-breaking contributions to public health, reproducing them in their original form and adding a commentary on their significance from a modern-day perspective. To complement the theme of this month's Bulletin, Thomas C. Quinn reviews the paper he co-authored in

Following its recognition in 1981, the HIV/AIDS epidemic has evolved to become the greatest challenge in global health, with some 34 million persons living with HIV worldwide. Early epidemiologic studies identified the major transmission routes of the virus before it was discovered, and enabled the implementation of prevention strategies. Although the first identified cases were in MSM in the United States and western Europe, the greatest impact of the epidemic has been in sub-Saharan Africa, where most of the transmission occurs between heterosexuals. Nine countries in southern Africa account for less than 2% of the world's population but now they represent about one third of global HIV infections. Where broadly implemented, HIV screening of donated blood and antiretroviral treatment (ART) of pregnant women have been highly effective in preventing transfusion-associated and perinatally acquired HIV, respectively. Access to sterile equipment has also been a successful intervention for injection drug users. Prevention of sexual transmission has been more difficult. Perhaps the greatest challenge in terms of prevention has been in the global community of MSM in which HIV remains endemic at high prevalence. The most promising interventions are male circumcision for prevention of female-to-male transmission and use of ART to reduce infectiousness, but the extent to which these interventions can be brought to scale will determine their population-level impact.