Human Immunodeficiency Virus/Syphilis Co-Infection in China: a Retrospective Observational Study

Syphilis is a common comorbidity among people living with human immunodeficiency virus (HIV). The factors that influence the occurrence of coinfection are not yet well understood.

We investigated the prevalence of syphilis and potential risk factors among people living with HIV (PLWH) in China from January 2018 to December 2022. Patients included were newly diagnosed, older than 18 years of age, and had first started standard antiretroviral therapy for HIV. All patients completed face-to-face questionnaire surveys and laboratory tests. Pearson’s Chi-square test was used to compare categorical variables and Student’s t-test was used to compare continuous variables. Logistic regression estimated the odds ratios and 95% CIs for associations between various factors and syphilis coinfection.

Among the 1391 patients with HIV, 1323 met the eligibility criteria. A total of 254 participants were coinfection with syphilis, with a prevalence of 19.20%. The prevalence of coinfection was highest in the illiterate/primary/junior high school group at 23.1% (95% confidence interval (CI),18.3–27.9%), followed by the high school group at 21.4% (95% CI, 16.4–26.4%), and the university/postgraduate group at 16.5% (95% CI, 13.9–19.2%). There was a significant difference in the number of sex partners between the HIV-infected and coinfection groups (5.8 ± 6.3 vs. 9.1 ± 11.3, p < 0.001). The prevalence of coinfection was higher in the CD₄ count < 200 group than in the CD₄ count > 400 group (p < 0.05). Anxiety scores in the coinfection group were also significantly higher than those in the non-coinfection group (p < 0.05). Logistic regression analyses found that below high school education (odds ratio (OR), 95% CI: 1.48, 1.11 ~ 1.97, p = 0.009), CD₄ count of less than 200 (OR, 95% CI: 1.45, 1.07 ~ 1.97, p = 0.016), five or more sexual partners (OR, 95% CI: 2.09, 1.58 ~ 2.78, p < 0.001), and anxiety (OR, 95% CI: 2.09, 1.58 ~ 2.78, p = 0.035) were more likely to exhibit coinfection.

Improving literacy levels, reducing the number of sexual partners, raising CD₄ levels, and reducing stress may help reduce the occurrence of syphilis in patients with HIV.

People living with HIV could benefit from increasing the frequency of syphilis testing for early detection and improving health education.