Increased gonorrhea detection highlights the need for additional prevention efforts. Gonorrhea may only be acquired when there is contact between infected and uninfected anatomical sites. With 3 sites of infection, this leads to 7 plausible routes of men who have sex with men (MSM) transmission: urethra-to-rectum, rectum-to-urethra, urethra-to-oropharynx, rectum-to-oropharynx, oropharynx-to-urethra, oropharynx-to-rectum, and oropharynx-to-oropharynx. We characterize the uncertainty and potential importance of transmission from each anatomical site using a deterministic compartmental mathematical model.
We developed a model of site-specific gonococcal infection, where individuals are infected at 0, 1, 2, or all 3 sites. Sexual behavior and infection duration parameters were fixed similar to a recent model analysis of Australian MSM. Markov chain Monte Carlo methods were used to sample the posterior distribution of transmission probabilities that were consistent with site-specific prevalence in American MSM populations under specific scenarios. Scenarios were defined by whether transmission routes may or may not transmit by constraining specific transmission probabilities to zero rather than fitting them.
Transmission contributions from each site have greater uncertainty when more routes may transmit; in the most extreme case, when all routes may transmit, the oropharynx can contribute 0% to 100% of all transmissions. In contrast, when only anal or oral sex may transmit, transmission from the oropharynx can account for only 0% to 25% of transmission. Intervention effectiveness against transmission from each site also has greater uncertainty when more routes may transmit.
Even under ideal conditions (ie, when site-specific gonococcal prevalence, relative rates of specific sex acts, and duration of infection at each anatomical site are known and do not vary), the relative importance of different anatomical sites for gonococcal infection transmission cannot be inferred with precision. Additional data informing per act transmissibility are needed to understand site-specific gonococcal infection transmission. This understanding is essential for predicting population-specific intervention effectiveness.
Using a mathematical model and sexually transmitted infection clinic data, we show that site-specific prevalence data (urethral, rectal, and oropharyngeal) are not sufficient to reveal the relative importance of gonococcal infection transmission routes.
From the *Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA;
†Department of Medicine, Beth Israel Deaconess Medical Center/Harvard Medical School and The Fenway Institute, Fenway Health, Boston, MA;
‡Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA; and
§Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM
Correspondence: Ian Spicknall, PhD, Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA. E-mail: email@example.com.
Acknowledgements: The assistance of Ken Levine and Chris Grasso of the Fenway Health Data Team are greatly appreciated.
Sources of Funding: ERS has been funded in whole or in part with Federal funds from the Centers for Disease Control and Prevention/OID/NCHHSTP/DSTDP, Department of Health and Human Services, under Interagency Agreement No. 17FED1710397.
Conflict of interest: None declared.
Disclaimer: The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
Received for publication September 17, 2018, and accepted November 11, 2018.
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