title: Transmission of HIV-1 during primary infection: relationship to sexual risk and sexually transmitted infections.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of GU Medicine, Brighton and Sussex University Hospitals, Brighton, UK.
authors.forename: David
authors.initials: D
authors.lastname: Pao
authors.forename: Martin
authors.initials: M
authors.lastname: Fisher
authors.forename: Stephane
authors.initials: S
authors.lastname: Hué
authors.forename: Gillian
authors.initials: G
authors.lastname: Dean
authors.forename: Gary
authors.initials: G
authors.lastname: Murphy
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Cane
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Sabin
authors.forename: Deenan
authors.initials: D
authors.lastname: Pillay
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D016000:Cluster Analysis; D005260:Female; D015658:HIV Infections / Q000453:epidemiology / Q000235:genetics / Q000635:transmission*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D011446:Prospective Studies; D012309:Risk-Taking; D012725:Sexual Behavior / Q000523:psychology*; D012747:Sexual Partners; D012749:Sexually Transmitted Diseases / Q000453:epidemiology*