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Original research
Modelling the impact of a sex work crackdown on syphilis transmission among female sex workers and their clients in South China
  1. Ngai Sze Wong1,2,3,
  2. Kimberly A Powers1,4,
  3. Joseph D Tucker1,2,5,
  4. Shui Shan Lee3,
  5. Beng Tin Goh6,7,
  6. Peizhen Zhao6,8,
  7. Lei Chen6,8,
  8. Cheng Wang6,8,
  9. Li Gang Yang6,8,
  10. Bin Yang6,8,
  11. Heping Zheng6,8,
  12. Shujie Huang6,8,
  13. Kate M Mitchell9
  1. 1 Institute for Global Health and Infectious Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
  2. 2 University of North Carolina Project-China, Guangzhou, Guangdong Province, China
  3. 3 Stanley Ho Centre for Emerging Infectious Diseases, Chinese University of Hong Kong, New Territories, Hong Kong
  4. 4 Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
  5. 5 SESH Global, Guangzhou, Guangdong, China
  6. 6 Southern Medical University Institute for Global Health and Sexually Transmitted Diseases, Guangzhou, Guangdong, China
  7. 7 Royal London Hospital, London, UK
  8. 8 Dermatology Hospital, Southern Medical University, Guangzhou, Guangdong, China
  9. 9 MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
  1. Correspondence to Shujie Huang, Guangdong Provincial Dermatology Hospital, Guangzhou, Guangdong, China 510095; huangshj_jm{at}


Objective To estimate the potential effects of an intense sex work crackdown on syphilis transmission in Guangdong Province, China.

Methods We developed a deterministic compartmental model of syphilis transmission among female sex workers (FSW) and their male clients in Guangdong Province, China. We based model assumptions on census data and scientific literature, and we fitted the model to sentinel surveillance estimates of syphilis prevalence (positive results in both treponemal and non-treponemal tests) among FSW between 2009 and 2013. We estimated the impact of an intense sex work crackdown in 2014 by comparing the number of new syphilis infections between 2014 and 2020 in crackdown versus basecase (no crackdown) scenarios. In modelling scenarios, we examined main crackdown mechanisms of impact, including changed number of FSW engaging in sex work, reduction of weekly transactions, condom usage rate and syphilis diagnosis rate.

Results In the basecase, predicted syphilis prevalence in FSW decreased from 2% in 2014 to 0.4% in 2020. In crackdown scenarios, syphilis incidence was predicted to transiently decrease and then to rebound relative to basecase levels a few years later. Shorter crackdowns led to higher, faster rebounds.

Conclusions Short-term intense crackdowns may exacerbate syphilis transmission among FSW and further marginalise an already vulnerable group. This study provides a quantitative, infection-related basis for changing sex work policies to reduce harms.

  • syphilis
  • mathematical model
  • policy

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  • Handling editor Laith J Abu-Raddad

  • Contributors NSW, KAP, JDT and SH designed the study. BTG, PZ, LC, CW, LGY, BY and HZ coordinated secondary data collection and interpretation of data for model parameterisation. NSW drafted the paper. NSW, KAP and KMM developed and validated the model. JDT and SH supervised the study. KAP, KMM, JDT, SH, SSL and BTG critically edited the manuscript. All authors approved the final manuscript.

  • Funding The research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Disclaimer The opinions expressed by the authors contributing to this journal do not necessarily reflect the opinions of the institutions with which the authors are affiliated.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval IRB approval was obtained from the Dermatology Hospital, Southern Medical University, China, and from the University of North Carolina at Chapel Hill (reference: 16-3148).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.