Different sampling strategies, analytic alternatives, and estimators have been proposed to better assess the characteristics of different hard-to-reach populations and their respective infection rates (as well as their sociodemographic characteristics, associated harms, and needs) in the context of studies based on respondent-driven sampling (RDS). Despite several methodological advances and hundreds of empirical studies implemented worldwide, some inchoate findings and methodological challenges remain. The in-depth assessment of the local structure of networks and the performance of the available estimators are particularly relevant when the target populations are sparse and highly stigmatized. In such populations, bottlenecks as well as other sources of biases (for instance, due to homophily and/or too sparse or fragmented groups of individuals) may be frequent, affecting the estimates. In the present study, data were derived from a cross-sectional, multicity RDS study, carried out in 12 Brazilian cities with transgender women (TGW). Overall, infection rates for HIV and syphilis were very high, with some variation between different cities. Notwithstanding, findings are of great concern, considering the fact that female TGW are not only very hard-to-reach but also face deeply-entrenched prejudice and have been out of the reach of most therapeutic and preventive programs and projects. We cross-compared findings adjusted using 2 estimators (the classic estimator usually known as estimator II, originally proposed by Volz and Heckathorn) and a brand new strategy to adjust data generated by RDS, partially based on Bayesian statistics, called for the sake of this paper, the RDS-B estimator. Adjusted prevalence was cross-compared with estimates generated by non-weighted analyses, using what has been called by us a naïve estimator or rough estimates.

Background: Gender-based discrimination remains a substantial barrier to health care access and HIV prevention among transgender women in Brazil. The aim of this study was to investigate the association between gender-based discrimination and medical visits, as well as with HIV testing among transgender women in the last 12 months in northeast Brazil. Methods: This is a cross-sectional study of 864 transgender women recruited using Respondent-Driven Sampling in three cities in northeastern Brazil in 2016. A socio-behavioral questionnaire was applied. Multivariate analyses were performed using logistic regression, with odds ratio and respective 95% confidence intervals estimation, to estimate the effect of gender-based discrimination on two outcomes: i) medical visits and ii) HIV testing in the last 12 months. Results: 547 transgender women (67·0%) had medical visits, and 385 (45·8%) underwent HIV testing in the last 12 months. In the multivariate analysis, gender-based discrimination was associated with a reduced likelihood of medical visits (OR: 0·29; 95%CI: 0·14–0·63) and HIV testing (OR: 0·41; 95%CI: 0·22–0·78) in the last 12 months. Conclusion: Gender-based discrimination played an essential role in reducing the access of TGW to medical visits and HIV testing services. Furthermore, by confirming the association between gender-based discrimination and medical visits and HIV testing in the multivariate analysis, we have demonstrated how this predictive variable can affect by reducing access to health services. The findings point to the need for non-discriminatory policies based on the defense and promotion of human rights that may foster the access of transgender women to Brazilian health services.

Chagas disease was investigated in four periurban areas of Ceará state, northeastern Brazil, through serological, parasitological and molecular methods in humans, reservoirs and vectors. A cross-sectional survey revealed a seroprevalence rate of 1.2% (13/1076 residents, six also proving positive through PCR). Trypanosoma cruzi infection was not detected in children under 10 years old. Triatoma pseudomaculata prevailed in the peridomiciles: 63 specimens, 69% (34/49) infected with trypanosomatids. Rhodnius nasutus was captured in Copernicia prunifera palm trees (n=280; 25.0% infected with trypanosomatids) and inside dwellings (n=8, all uninfected). Trypanosoma cruzi seropositive reservoirs, represented by Didelphis albiventris (n=27), Rattus rattus (n=24), Thrichomys laurentius (n=2), Mus musculus (n=1) and Monodelphis domestica (n=1), were identified. Among domestic dogs (n=96) seroprevalence reached 21.9%. Miniexon multiplex PCR assays characterized TcI in triatomines. Both TcI and TcII were detected in wild mammal hosts. We conclude that Trypanosoma cruzi circulates within a domestic zoonotic cycle, requiring continuous surveillance. Insecticide application to domiciles does not appear to prevent continuous reintroduction of wild triatomine specimens, presenting a challenge to authorities involved in Chagas disease control.

Background: The 2022 multicountry mpox outbreak positioned the condition as a public health emergency of international concern. By May 2023, Brazil ranked second globally in the cumulative number of mpox cases and deaths. The higher incidence of mpox among gay and other men who have sex with men in the current mpox outbreak deepens the stigma and discrimination against sexual and gender minorities (SGM). This might worsen the structural barriers impacting access to health services, which ultimately leads to undertesting and underreporting of cases. There are no data available on mpox knowledge and stigma in Latin America. Objective: We aimed to evaluate mpox knowledge, stigma, and willingness to vaccinate for mpox among SGM, and to describe sociodemographic and behavioral characteristics according to self-reported mpox diagnosis. Methods: A cross-sectional, internet-based survey was conducted in a convenience sample of adults (aged >18 years) living in Brazil recruited through advertisements on dating apps, social media, referral institutions for infectious diseases websites, and mass media (October-November 2022). We compared participants’ characteristics according to self-reported mpox diagnosis using chi-square test or Fisher exact test for qualitative variables and Kruskal-Wallis test for quantitative variables. Results: We enrolled 6236 participants: 5685 (91.2%) were cisgender men; 6032 (96.7%) were gay, bisexual, or pansexual; 3877 (62.2%) were White; 4902 (78.7%) had tertiary education; and 4070 (65.2%) reported low or middle income. Most participants (n=5258, 84.4%) agreed or strongly agreed that “LGBTQIA+ individuals are being discriminated and stigmatized due to mpox.” Mpox awareness was 96.9% (n=6044), and 5008 (95.1%) were willing to get vaccinated for mpox. Overall, 324 (5.2%) reported an mpox diagnosis. Among these, 318 (98.1%) reported lesions, 178 (56%) local pain, and 316 (99.4%) sought health care. Among participants not reporting a diagnosis, 288 (4.9%) had a suspicious lesion, but only 158 (54.9%) of these had sought health care. Compared to participants with no diagnosis, those reporting an mpox diagnosis were younger (P<.001), reported more sex partners (P<.001), and changes in sexual behavior after mpox onset (P=.002). Moreover, participants diagnosed with mpox reported more frequently being tested for HIV in the prior 3 months (P<.001), living with HIV (P<.001), currently using HIV pre-exposure prophylaxis (P<.001), and previous sexually transmitted infection diagnosis (P<.001). Conclusions: Our results point to high mpox knowledge and willingness to vaccinate among SGM in Brazil. Participants self-reporting mpox diagnosis more frequently reported to be living with HIV, STI diagnosis, and current pre-exposure prophylaxis use, highlighting the importance of an mpox assessment that includes comprehensive sexual health screenings. Efforts to decrease stigma related to mpox among SGM are necessary to avoid mpox underdiagnosis.

By October 30, 2022, 76,871 cases of mpox were reported worldwide, with 20,614 cases in Latin America. This study reports characteristics of a case series of suspected and confirmed mpox cases at a referral infectious diseases center in Rio de Janeiro, Brazil. This was a single-center, prospective, observational cohort study that enrolled all patients with suspected mpox between June 12 and August 19, 2022. Mpox was confirmed by a PCR test. We compared characteristics of confirmed and non-confirmed cases, and among confirmed cases according to HIV status using distribution tests. Kernel estimation was used for exploratory spatial analysis. Of 342 individuals with suspected mpox, 208 (60.8%) were confirmed cases. Compared to non-confirmed cases, confirmed cases were more frequent among individuals aged 30-39 years, cisgender men (96.2% vs. 66.4%; p < 0.0001), reporting recent sexual intercourse (95.0% vs. 69.4%; p < 0.0001) and using PrEP (31.6% vs. 10.1%; p < 0.0001). HIV (53.2% vs. 20.2%; p < 0.0001), HCV (9.8% vs. 1.1%; p = 0.0046), syphilis (21.2% vs. 16.3%; p = 0.43) and other STIs (33.0% vs. 21.6%; p = 0.042) were more frequent among confirmed mpox cases. Confirmed cases presented more genital (77.3% vs. 39.8%; p < 0.0001) and anal lesions (33.1% vs. 11.5%; p < 0.0001), proctitis (37.1% vs. 13.3%; p < 0.0001) and systemic signs and symptoms (83.2% vs. 64.5%; p = 0.0003) than non-confirmed cases. Compared to confirmed mpox HIV-negative, HIV-positive individuals were older, had more HCV coinfection (15.2% vs. 3.7%; p = 0.011), anal lesions (45.7% vs. 20.5%; p < 0.001) and clinical features of proctitis (45.2% vs. 29.3%; p = 0.058). Mpox transmission in Rio de Janeiro, Brazil, rapidly evolved into a local epidemic, with sexual contact playing a crucial role in its dynamics and high rates of coinfections with other STI. Preventive measures must address stigma and social vulnerabilities. Instituto Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz (INI-Fiocruz).