Syphilis continues to be a public health problem worldwide and its incidence has increased in people living with HIV/AIDS in recent years. This study determined the prevalence and factors associated with syphilis in people living with HIV/AIDS in the city of Belém, northern Brazil. A cross-sectional study was conducted from June to November 2018. A total of 500 people living with HIV/AIDS attended at a specialized unit of the public health network of the State of Pará were studied. Questionnaires were used to collect socio-demographic data and potential risk factors for syphilis. Blood samples were collected from all subjects and screened for syphilis using VDRL, and the seropositive were confirmed using FTA-abs. Logistic regressions were used to identify the factors associated with syphilis. Most subjects were male (56.8%), had more than 40 years (54.0%), single (63.0%), had finished high school (54.2%), had monthly income ≤1 minimum wage (72.4%), and had been born to the city of Belém (59.8%). Prevalence of syphilis was 6.4%. Eight characteristics/behaviors associated with syphilis: male, young adults, single, studied at least high school, monthly income >1 minimum wage, homosexual/bisexual, does not use or sporadically use condoms during sexual intercourse, and have had more than one sexual partner in the last three months. The prevalence of syphilis in people living with HIV/AIDS in Belém is low when compared to other Brazilian states. However, there is a need for public policies and actions to monitor, control and prevent these two sexually transmitted infections.

Chlamydia trachomatis is one of the most prevalent sexually transmitted bacteria worldwide and may increase the risk of other sexually transmitted infections (STIs) including the human immunodeficiency virus (HIV). This study describes the seroprevalence of C. trachomatis infection among antiretroviral-naïve patients who are newly diagnosed with HIV in the city of Belém, Pará, in the Amazon region of Brazil. A cross-sectional study was carried out between January 2018 and January 2019 in 141 people living with HIV/AIDS (PLHA) who were followed up in a specialized unit of the public health network of Pará. The investigation of IgG antibodies against C. trachomatis was performed by enzyme immunoassay. Sociodemographic and sexual behavior information were obtained through a questionnaire. The prevalence of IgG anti-C. trachomatis antibodies was 64.8% (92/141). The majority of individuals were young, heterosexual, single men who did not use condoms during sexual intercourse and had no history of STIs. No significant differences were found when comparing any clinical or demographic data between groups. Our results demonstrated a high rate of exposure to C. trachomatis in newly diagnosed HIV-infected individuals in the Amazon region of Brazil, and all PLHA should be screened for C. trachomatis to decrease transmission of the bacteria and prevent the clinical manifestations of chronic infection.