Giving syphilis and gonorrhea to friends: Using in-person friendship networks to find additional cases of gonorrhea and syphilis

BACKGROUND: Syphilis and gonorrhea reached an all-time high in 2018. The resurgence of syphilis and gonorrhea requires innovative methods of sexual contact tracing that encourage disclosure of same-sex sexual contacts that might otherwise be suppressed. Over 75% of Grindr mobile phone application users report seeking “friendship,” so this study asked people diagnosed with syphilis and gonorrhea to identify their friends. METHODS: Patients at the two Baltimore sexually transmitted infection (STI) clinics and the Baltimore City Health Department were asked 12 questions to elicit members of their friendship networks before eliciting sexual networks. The study included 353 index cases and 172 friendship contacts, yielding a friendship network of 331 non-isolates (n=331) and sexual-only network of 140 non-isolates. The data were plotted and analyzed using exponential family random graph analysis. RESULTS: Eliciting respondents’ in-person social contacts yielded 12 syphilis cases and 6 gonorrhea cases in addition to the 16 syphilis cases and 4 gonorrhea cases that would have been found with sexual contacts alone. Syphilis is clustered within sexual (odds ratio=2.2, 95% confidence interval (1.36, 3.66)) and social contacts (OR=1.31,95% CI (1.02, 1.68)). Gonorrhea is clustered within reported social (OR=1.56, 95% CI (1.22, 2.00)) but not sexual contacts (OR=0.98, 95% CI (0.62, 1.53)). CONCLUSIONS: Eliciting friendship networks of people diagnosed with syphilis and gonorrhea may find members of their sexual networks, drug use networks, or people of similar STI risk. Friendship networks include more diagnosed cases of syphilis and gonorrhea than sexual networks alone, especially among populations with many non-disclosing men who have sex with men (MSM) and women who have sex with women (WSW). Future research should evaluate whether this friendship network method of contact tracing can be implemented by adapting automated mobile phone COVID-19 contact tracing protocols, if these COVID-19 contact tracing methods are able to maintain anonymity and public trust.