How Many HIV infections may be averted by targeting primary infection in men who have sex with men? Quantification of changes in transmission-risk behavior, using an individual-based model.
In the United Kingdom, human immunodeficiency virus (HIV) transmission among men who have sex with men (MSM) is not under control, despite readily available treatment, highlighting the need to design a cost-effective combination prevention package. MSM report significantly reduced transmission risk behavior following HIV diagnosis. To assess the effectiveness of HIV diagnosis in averting transmission during highly infectious primary HIV infection (PHI), we developed a stochastic individual-based model to calculate the number of HIV-transmission events expected to occur from a cohort of recently infected MSM with and those without the behavior changes reported after diagnosis. The model incorporates different types of sex acts, incorporates condom use, and distinguishes between regular and casual sex partners. The impact on transmission in the 3 months after infection depends on PHI duration and testing frequency. If PHI lasts for 3 months and testing is performed monthly, then behavior changes after diagnosis would have reduced estimated transmission events by 49%-52%, from 31-45 to 15-23 events; a shorter duration of PHI and/or a lower testing frequency reduces the number of infections averted. Diagnosing HIV during PHI can markedly reduce transmission by changing transmission-risk behavior. Because of the high infectivity but short duration of PHI, even short-term behavior change can significantly reduce transmission. Our quantification of the number of infections averted is an essential component of assessment of the cost-effectiveness of strategies to increase detection and diagnoses of PHI.
MRC Centre for Outbreak Analysis and Modelling NIHR Health Protection Research Unit in Modelling Methodology Department of Infectious Disease Epidemiology Modelling and Economics Unit, Public Health England Centre for Infectious Disease Surveillance and Control.
Peter J
PJ
White
Department of HIV, Faculty of Medicine, Guys and St Thomas' NHS Trust / Kings College London, United Kingdom.
Julie
J
Fox
Department of Genitourinary Medicine and Infectious Disease, Faculty of Medicine, Imperial College London.
Jonathan
J
Weber
Department of Genitourinary Medicine and Infectious Disease, Faculty of Medicine, Imperial College London.
Sarah
S
Fidler
Department of Infectious Disease Epidemiology.
Helen
H
Ward
D000328:Adult; D000465:Algorithms; D015658:HIV Infections / Q000453:epidemiology / Q000517:prevention & control* / Q000635:transmission; D018451:Homosexuality, Male; D006801:Humans; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015995:Prevalence; D012309:Risk-Taking; D047568:Unsafe Sex; D055815:Young Adult
HIV transmission risk; behavior change; counseling; diagnosis; infections averted; mathematical model; men who have sex with men; primary HIV infection