This was a cross-sectional internet-based survey conducted in a convenience sample of adults (aged ≥18 years) living in Brazil, who were recruited through advertisements on dating apps (Grindr and Scruff), social media (Facebook and Instagram), referral institutions for infectious diseases websites or social media (Instituto Nacional de Infectologia Evandro Chagas and Fundação Oswaldo Cruz), radio, and mass media from October to November 2022. Banners in Scruff and Grindr and boosted posts on Facebook and Instagram, as in prior work [17,18], were used to recruit individuals to complete a voluntary open survey in Portuguese, with all items including a nonresponse option. The survey was programmed on Alchemer. Respondents were able to change or review answers and did not receive any compensation. Usability and technical functionality in different personal computers and mobile phone operating systems were confirmed before survey administration. We excluded respondents who did not reach the end of the survey and those who incorrectly answered any of the 5 attention questions [19]. Only 1 response per IP address was allowed.

HIV self-reported status was derived from the question “Have you ever had an HIV test?” with potential responses positive, negative, or never (“unknown”). Participants were asked when the last HIV test was (≤3, >3-6, and >6 months). People living with HIV answered questions about the time since the diagnosis (≤6, >6-12, and >12 months), about antiretroviral therapy (ART) use, ART adherence using a validated scale [23], and if they currently had an undetectable HIV viral load (yes or no). Participants self-reporting negative or unknown status were asked about HIV pre-exposure prophylaxis (PrEP) use (never, current, or past) and adherence (rated from 0 [missed all doses in past 30 days] to 100 [no missing dose]). We dichotomized complete PrEP adherence (rating=100) into yes or no.

Participants were asked about syphilis, gonorrhea, and chlamydia diagnoses since June 2022 (yes or no), hepatitis B vaccination (no, 1-2 doses, 3 doses, and did not remember), and ever tested positive for hepatitis C (yes or no).

Participants responded to questions regarding participation in vaccination campaigns (always, sometimes, or never) and whether they had been vaccinated for COVID-19 and mpox. We used a 4-point Likert scale to access the willingness to use an mpox preventive vaccine, which was defined as responding highly likely to the question: “Would you vaccinate against mpox?” following other studies evaluating the willingness to use biomedical technologies [24,25]. We also accessed willingness to participate in research studies to evaluate: (1) mpox preventive vaccine; (2) mpox preventive drug; and (3) mpox therapeutic drug.

The Reactions to Homosexuality Scale (RHS), originally developed to measure internalized homonegativity among MSM, includes 7 items measured on a 7-point Likert scale from strongly disagree to strongly agree, with total scores ranging from 0 to 42 [18,26]. For this analysis, we adapted the scale to allow completion by all SGM, as described in Table S1 in Multimedia Appendix 1. Higher RHS scores indicate higher internalized lesbian, gay, bisexual, transgender, queer, intersex, asexual, plus (LGBTQIA+) phobia. We also asked participants to rate mpox stigma toward LGBTQIA+ people on a 7-point Likert scale from strongly disagree to strongly agree: “LGBTQIA+ individuals are being discriminated and stigmatized due to mpox.”

Our main outcome was self-reported mpox diagnosis, defined as a positive answer to the question: “Have you been diagnosed with mpox by a health professional?”

We performed an exploratory analysis based on the kernel estimator, with adaptive radius and Gaussian function, to obtain an overview of the spatial distribution of the points corresponding to individuals with confirmed and nonconfirmed mpox diagnosis and identifying potential outbreaks of occurrence. The zip codes were considered for georeferencing.

Continuous variables were described by their median and IQR and mean and SD. We compared sociodemographic, behavior, and clinical characteristics according to self-reported mpox diagnosis (yes vs no) using a chi-square test or Fisher exact test for qualitative variables and a Kruskal-Wallis test for quantitative variables. All analyses were performed using R software (version 4.2.2; R Foundation for Statistical Computing).

This study received approval from the institutional review board at the Instituto Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz (#CAAE 61290422.0.0000.5262). All study participants provided electronic informed consent before survey initiation.

This analysis describes the results of a large web-based survey in Brazil conducted during the mpox surge in 2022. Respondents were mostly MSM from metropolitan regions, with a 5.6% prevalence of self-reported mpox diagnosis, which is slightly higher than Brazilian surveillance numbers. This indicates that our survey may have reached populations most affected by mpox by the current outbreak [2,5,6]. There were no reported cases among transgender women, which highlights the low mpox burden in this group, in agreement with Brazilian official data available, disaggregated by gender [8,27]. Our findings point to a high awareness of mpox among SGM, with the internet and television as the most frequent information sources. This underscores the importance of adequate science communication through traditional and innovative means of communication and the need to stop fake news that contributes to misleading information as well as reinforces stigma [28]. Most participants agreed or strongly agreed that LGBTQIA+ individuals are being discriminated against and stigmatized due to mpox. To our knowledge, this is the first study to describe mpox awareness, willingness to vaccinate for mpox, and self-reported prevalence of mpox in Latin America.

Willingness to use mpox vaccine and to follow social isolation if required were high, suggesting an adequate understanding of the importance of public health measures to successfully mitigate the impact of the mpox outbreak among SGM. While countries in North America and Western Europe initiated mpox vaccination of the most affected population (MSM) by mid-2022, mpox vaccination in Brazil only started in March 2023. Due to the low number of vaccine units available, vaccination in the country is restricted to very few groups such as people living with HIV, health professionals working with Orthopoxvirus (pre-exposure vaccination), and those who had contact with fluids and secretions of persons with suspected mpox (postexposure vaccination) [29].

In our study, individuals with self-reported mpox diagnosis more frequently referred to mucocutaneous, genital or anal lesions, coinfection with hepatitis C, and local pain. These clinical characteristics are in agreement with global and national data [2,6,30]. Local pain was the most frequent reason for hospitalization in a cohort in Rio de Janeiro State, Brazil [6]. This is critical in the context of poor outcomes related to pain control according to gender, sexual orientation, and race, which might deepen mpox-related stigma and increase the gap between the most vulnerable populations and health services [31,32].

Among respondents with no mpox diagnosis, a substantial proportion did not seek health care assistance despite reporting mpox suspicious lesions or symptoms. Avoidance of health services is common among SGM and directly linked to stigma, discrimination, and structural barriers faced by these groups [33,34]. This might lead to the underreporting of mpox cases in highly discriminatory settings, such as Brazil. In addition, participants with a self-reported mpox diagnosis also reported following a higher frequency of health measures (eg, HIV care and testing, STI diagnosis, and PrEP use) and lower rates of internalized LGBTQIA+ phobia. This might indicate that individuals who sought an mpox diagnosis most commonly have access to health services in general. Furthermore, these participants might have previous links with gender-competent health care services and more access to health information, all potentially related to a lower perceived gender and sexual orientation–based discrimination.

Although participants with an mpox diagnosis reported a higher number of sexual partners, binge drinking before sex, chemsex, substance use, and higher frequency to sex venues, they also adopted more changes in sexual behavior after the mpox outbreak, possibly due to higher awareness and feelings of fear and hopelessness related to mpox. This finding is in agreement with previous surveys conducted in the United States among the most vulnerable populations [16,35]. Moreover, most individuals with an mpox diagnosis in our survey also reported sex with other cisgender men, reinforcing the role of highly interconnected and dense sexual networks in the mpox transmission dynamics [36]. Even among participants who self-reported an mpox diagnosis, only a small proportion reported a partner with suspected or confirmed mpox. Although this observation might be related to underdiagnosed cases, it raises concerns about the potential role of subclinical infections in mpox transmission dynamics, while it also reflects the well-known challenges in STI network mapping [37-39].

People living with HIV enrolled in the current analysis reported low ART adherence (895/1473, 60.8%). Regardless of mpox diagnosis, this reinforces the urgent need to better monitor the HIV care continuum. In the context of mpox, advanced immunosuppression and poor ART adherence have been associated with worse mpox clinical outcomes, including mpox-related hospitalization and death [40]. The high rates of other STIs occurring concomitantly with mpox highlight the importance of a comprehensive screening at mpox assessment, in accordance with the well-established rationale that 1 STI diagnosis implies a higher likelihood of coinfection with an additional one [41].

Our study has some limitations. First, the cross-sectional study design hinders identifying causal associations. In addition, all responses were self-reported, thus introducing the possibility of recall, response, or social desirability bias. Moreover, our sample constitutes a highly educated, middle or high socioeconomic status subset of Brazilian persons with access to a device compatible with GSN apps, although cellphones and internet connection have been shown to be widely available in all socioeconomic strata in Brazil [42]. Transgender women are often a highly vulnerable group in Brazil with lower access to the internet, which may have impacted their recruitment using web-based strategies as previously observed [17].

Our results point to high mpox knowledge and willingness to vaccinate for mpox among SGM in Brazil. Participants self-reporting mpox diagnosis more frequently reported to be living with HIV, STI diagnosis, and current PrEP use. Our findings highlight the importance of an mpox assessment that includes comprehensive sexual health screenings. Efforts to decrease stigma related to mpox among SGM is necessary to avoid mpox underdiagnosis.