Epidemiology of primary HIV-1 infection.

Purpose Of Review: To review recent studies reporting epidemiological and public health aspects of primary and recently acquired HIV infection, with a particular emphasis on patterns of occurrence, relationship to onward transmission, diagnostic strategies and risk factors.

Recent Findings: Diagnosis of primary HIV infection remains a relatively infrequent occurrence. Clinical and demographic characteristics may be helpful indicators to guide the decision to offer testing. The high levels of viraemia associated with primary HIV infection represent a particular risk of onward transmission, as recently demonstrated through studies using genotyping methods to link newly acquired cases. Diagnostic strategies involving nucleic acid detection have been increasingly used to identify cases prior to the development of antibodies. Serological tests for early infection are valid for epidemiological purposes but are not generally viewed reliable enough for individual diagnosis. Prospective studies continue to be a useful means of identifying factors associated with the risk of newly acquired HIV infection, and can guide the implementation and evaluation of prevention strategies.

Summary: The occurrence of primary HIV infection is an event of public health importance. Understanding of the extent of primary HIV infection and its risk factors in populations can guide the development and evaluation of preventive interventions.