title: Human immunodeficiency virus transmission at each step of the care continuum in the United States.
abstract: OBJECTIVE
  Human immunodeficiency virus (HIV) transmission risk is primarily dependent on behavior (sexual and injection drug use) and HIV viral load. National goals emphasize maximizing coverage along the HIV care continuum, but the effect on HIV prevention is unknown.
  
  
  OBJECTIVE
  To estimate the rate and number of HIV transmissions attributable to persons at each of the following 5 HIV care continuum steps: HIV infected but undiagnosed, HIV diagnosed but not retained in medical care, retained in care but not prescribed antiretroviral therapy, prescribed antiretroviral therapy but not virally suppressed, and virally suppressed.
  
  
  METHODS
  A multistep, static, deterministic model that combined population denominator data from the National HIV Surveillance System with detailed clinical and behavioral data from the National HIV Behavioral Surveillance System and the Medical Monitoring Project to estimate the rate and number of transmissions along the care continuum. This analysis was conducted January 2013 to June 2014. The findings reflect the HIV-infected population in the United States in 2009.
  
  
  METHODS
  Estimated rate and number of HIV transmissions.
  
  
  RESULTS
  Of the estimated 1,148,200 persons living with HIV in 2009, there were 207,600 (18.1%) who were undiagnosed, 519,414 (45.2%) were aware of their infection but not retained in care, 47,453 (4.1%) were retained in care but not prescribed ART, 82,809 (7.2%) were prescribed ART but not virally suppressed, and 290,924 (25.3%) were virally suppressed. Persons who are HIV infected but undiagnosed (18.1% of the total HIV-infected population) and persons who are HIV diagnosed but not retained in medical care (45.2% of the population) were responsible for 91.5% (30.2% and 61.3%, respectively) of the estimated 45,000 HIV transmissions in 2009. Compared with persons who are HIV infected but undiagnosed (6.6 transmissions per 100 person-years), persons who were HIV diagnosed and not retained in medical care were 19.0% (5.3 transmissions per 100 person-years) less likely to transmit HIV, and persons who were virally suppressed were 94.0% (0.4 transmissions per 100 person-years) less likely to transmit HIV. Men, those who acquired HIV via male-to-male sexual contact, and persons 35 to 44 years old were responsible for the most HIV transmissions by sex, HIV acquisition risk category, and age group, respectively.
  
  
  CONCLUSIONS
  Sequential steps along the HIV care continuum were associated with reduced HIV transmission rates. Improvements in HIV diagnosis and retention in care, as well as reductions in sexual and drug use risk behavior, primarily for persons undiagnosed and not receiving antiretroviral therapy, would have a substantial effect on HIV transmission in the United States.
authors.affiliation: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Jacek
authors.initials: J
authors.lastname: Skarbinski
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia.
authors.forename: Eli
authors.initials: E
authors.lastname: Rosenberg
authors.affiliation: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Paz-Bailey
authors.affiliation: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: H Irene
authors.initials: HI
authors.lastname: Hall
authors.affiliation: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Rose
authors.affiliation: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Abigail H
authors.initials: AH
authors.lastname: Viall
authors.affiliation: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Fagan
authors.affiliation: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Amy
authors.initials: A
authors.lastname: Lansky
authors.affiliation: National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Mermin
mesh_terms: D000328:Adult; D000368:Aged; D019380:Anti-HIV Agents / Q000008:administration & dosage*; D003266:Continuity of Patient Care; D018562:Disease Transmission, Infectious / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology / Q000635:transmission*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011159:Population Surveillance; D012309:Risk-Taking; D012725:Sexual Behavior; D015819:Substance Abuse, Intravenous / Q000150:complications; D014481:United States / Q000453:epidemiology; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents