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Transmission of HIV-1 during primary infection: relationship to sexual risk and sexually transmitted infections

Pao, Davida; Fisher, Martina; Hué, Stephaneb,e; Dean, Gilliana; Murphy, Garye; Cane, Patricia Ad,e; Sabin, Caroline Ac; Pillay, Deenanb,e

Epidemiology and Social: Concise Communication

Objective: To study primary HIV-1 infections (PHI) using molecular and epidemiological approaches in order to assess correlates of transmission in this population.

Methods: Individuals with PHI were recruited prospectively from a discrete cohort of 1235 individuals under follow-up in a well-defined geographical area between 1999 and 2003. PHI was diagnosed by one of the following: negative HIV antibody test within 18 months, evolving antibody response, or application of the serological testing algorithm for recent HIV seroconversion. The pol gene was sequenced to identify genotypic resistance and facilitate molecular epidemiological analysis. Clinical data were collected and linked in an irretrievable fashion when informed consent was obtained.

Results: A total of 103 individuals with PHI diagnosed between 1999 and 2003 were included in the study; 99 (96%) were male and 90 (91%) were men who have sex with men. Viruses from 35 out of 103 (34%) appeared within 15 phylogenetically related clusters. Significant associations with clustering were: young age, high CD4 cell count, number of sexual contacts, and unprotected anal intercourse (UAI) in the 3 months before diagnosis (P < 0.05 for all). High rates of acute sexually transmitted infections (STI) were observed in both groups with a trend towards higher rates in those individuals with viruses within a cluster (42.9 versus 27.9%; P = 0.13).

Conclusion: High rates of partner change, UAI and STI are factors that facilitate onward transmission during PHI. More active identification of individuals during PHI, the management of STI and highly active antiretroviral therapy may all be useful methods to break transmission networks.

aDepartment of GU Medicine, Brighton and Sussex University Hospitals, Brighton, UK

bCentre of Virology, Division of Infection and Immunity

cDepartment of Primary Care and Population Sciences, Royal Free and University College Medical School, University College London, London, UK

dHPA Antiviral Susceptibility Reference Unit, University of Birmingham Medical School, and Birmingham HPA, Heartlands Hospital, Birmingham, UK

eCentre for Infections, Health Protection Agency, Colindale, UK

Received 22 June, 2004

Revised 20 September, 2004

Accepted 7 October, 2004

Correspondence to Deenan Pillay, Centre of Virology, Division of Infection and Immunity, Royal Free and University College Medical School, Windeyer Institute, 46 Cleveland Street, London W1P 6DF, UK. E-mail:

© 2005 Lippincott Williams & Wilkins, Inc.