The legal and social environment for sex workers must be addressed alongside medical interventions to stop the spread of HIV, researchers say.

Mathematical modelling work by Drs Michael Pickles and Marie-Claude Boily from Imperial College London estimates that decriminalising sex work could prevent up to 33 to 46 per cent of HIV infections among female sex workers (FSWs) and clients worldwide over the next decade.

The international study looked at how the legal, social, and political environments in which people who sell sex live and work – which the researchers call “structural determinants” – influences the HIV epidemic. It was part of a series of papers on HIV and sex workers published in The Lancet this week and presented at the International Aids Conference in Melbourne.

The researchers collected all the available data on HIV prevalence, condom use and structural determinants among sex workers, and used a mathematical model to simulate the effect of different interventions in three contrasting settings: Vancouver, Canada; Bellary, India; and Mombasa, Kenya.

The research shows that eliminating sexual violence could reduce HIV infection rates among FSWs and their clients by up to a fifth over 10 years in the settings investigated, through its immediate and sustained effect on non-condom use. In Kenya, improving access to antiretroviral therapy for FSWs and clients could prevent around 34 per cent of HIV infections among them in the next decade.

However, the study shows that decriminalisation of sex work could have the greatest effect on the course of HIV epidemics across all settings studied. Within a criminalised environment, sexual violence is prevalent and has a negative effect on condom use. It forces sex workers to work in unsafe environments that promote high-risk behaviour.  Sex workers also experience police harassment, which also increases HIV risk by forcing them to rush transactions and forgo condoms, and preventing them from reporting violence to authorities.

Previous research suggests that in low- and middle-income countries, the risk of HIV infection is 13.5 times higher for female sex workers than women in the general population.

Calls for removal of all legal restrictions targeting sex work have been supported by international policy bodies, including WHO, UNAIDS, UNDP, and the UN Population Fund.

Dr Kate Shannon, first author of the study at the University of British Columbia, said: “Our findings clearly show that structural factors remain paramount to an effective HIV response in sex work. Governments and policy makers can no longer ignore the evidence that decriminalisation will protect health and human rights of sex workers “

Dr Marie-Claude Boily, senior author of the study at the School of Public Health, Imperial College London said: “To observe the level of impact we predict, we need not only decriminalisation of sex work but also to have necessary and sufficient clinical services, prevention interventions and psychosocial support in place and easily accessible to sex workers.”   

Reference: Kate Shannon, Steffanie A Strathdee, Shira M Goldenberg, Putu Duff, Peninah Mwangi, Maia Rusakova, Sushena Reza-Paul, Joseph Lau, Kathleen Deering, Michael R Pickles, Marie-Claude Boily. ‘Global epidemiology of HIV among female sex workers: influence of structural determinants.’ The Lancet, Published online 22 July 2014 http://dx.doi.org/10.1016/S0140-6736(14)60931-4

Photo: “Shanghai, Prostitutes in back alleys” by Lei Han on Flickr. Some rights reserved