title: MSM: resurgent epidemics.
abstract: OBJECTIVE
  The present review discusses the recent finding on behavioral risk factors for HIV transmission from cohort studies in MSM.
  
  
  RESULTS
  HIV incidence among MSM has been increasing in many countries around the world. Some data support early detection and widespread use of antiretroviral treatment (ART) to decrease HIV incidence. However, suboptimal ART adherence could lead to relapse of viremia and new transmission events. Condom use for unprotected anal sex among MSM remains an important prevention tool, but use remains low in many parts of the world. Seroadaptive behaviors by MSM, such as serosorting, may also decrease condom use. However, when serosorting is practiced by MSM who receive frequent HIV testing, the risk of HIV acquisition is reduced. Serosorting and other characteristics of sexual networks, such as concurrency, may be major determinants of transmission for HIV and sexually transmitted infections among MSM. Worldwide, detailed evaluation of the factors related to rising MSM HIV incidence, as well as access to testing and care, is limited by stigma and criminalization of HIV and homosexuality.
  
  
  CONCLUSIONS
  Cohort studies of MSM remain an important strategy to characterize the behavioral factors that drive HIV transmission and how use of ART for prevention and treatment may affect both the risk of HIV transmission and acquisition by MSM.
authors.affiliation: Department of Medicine, University of California, San Diego, California 92103, USA.
authors.forename: Sheldon R
authors.initials: SR
authors.lastname: Morris
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Little
mesh_terms: D019380:Anti-HIV Agents / Q000627:therapeutic use*; D015331:Cohort Studies; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000635:transmission*; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D008297:Male; D012307:Risk Factors; D012725:Sexual Behavior / Q000706:statistics & numerical data; D016903:Drug Monitoring
chemical_list: D019380:Anti-HIV Agents