title: What do mathematical models tell us about the emergence and spread of drug-resistant HIV?
abstract: OBJECTIVE
  To discuss recent HIV epidemic models examining the transmission of antiretroviral (ARV) drug resistance.
  
  
  RESULTS
  A relatively small number of recent transmission models have investigated ARV resistance in the context of therapeutic, combined ART (cART); ARV-vaginal microbicides (ARV-VMB); and oral pre-exposure prophylaxis (PrEP). Models of cART use have highlighted potential concerns about future resistance transmission, particularly in resource-constrained settings, and have emphasized the benefits of viral load monitoring in limiting resistance spread. PrEP models have concluded that inadvertent use by HIV-infected individuals could increase resistance prevalence, and that risk compensation by PrEP users could limit their beneficial effects on HIV transmission. ARV-VMB models have demonstrated that whereas resistance can reduce prophylactic effectiveness in preventing HIV acquisition of female ARV-VMB users, it may concomitantly benefit users' male partners if the resistant strains that female users acquire are less transmissible than wild-type strains. The models have examined the balance between these two factors at the population level.
  
  
  CONCLUSIONS
  Recent HIV transmission models have adopted a wide assortment of structures and assumptions to explore drug resistance in the context of different ARV interventions in various settings. There is a need for future work emphasizing the simultaneous effects of multiple ARV interventions, as well as the public health impact of resistance, not just its prevalence.
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College London, UK. r.baggaley@imperial.ac.uk
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: Baggaley
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Powers
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Boily
mesh_terms: D019380:Anti-HIV Agents / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D005260:Female; D006678:HIV / Q000187:drug effects* / Q000302:isolation & purification; D015658:HIV Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000635:transmission / Q000821:virology*; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D014481:United States
chemical_list: D019380:Anti-HIV Agents