Testing the limits of case finding for HIV prevention.

HIV testing technologies have been available for two decades, but concerns about stigma and discrimination have historically tempered the application of case finding-a cornerstone of public-health practice-to combat the HIV/AIDS pandemic. The recent expansion of access to HIV treatment has resulted in a shift of emphasis from pairing testing with rigorous risk-reduction prevention counselling, to applying testing to find infected individuals, address their care and treatment needs, and prevent them from infecting others. However, the efficacy of case finding for infectious disease prevention is contingent on two basic principles: the ability to identify infected individuals before further transmission occurs, and the availability of effective strategies to prevent such transmission from taking place. Although there is evidence that specific approaches to HIV counselling and testing can support behaviour change, both high infectivity during early HIV infection and specific sexual network structures could combine to substantially limit our ability to identify cases before ongoing transmission occurs. Facilitating the broader adoption of prevention behaviours therefore remains essential to prevent the continued spread of HIV.