Innovating a Community-driven Enumeration and Needs Assessment of People Experiencing Homelessness: A Network Sampling Approach for the HUD-Mandated Point-in-Time Count.

To enumerate people experiencing homelessness in the U.S., the federal Department of Housing and Urban Development (HUD) mandates its designated local jurisdictions regularly conduct a crude census of this population. This Point-in-Time (PIT) body count, typically conducted on a January night by volunteers with flashlights and clipboards, is often followed by interviews with a separate convenience sample. Here, we propose employing a network-based (peer-referral) respondent-driven sampling (RDS) method to generate a representative sample of unsheltered people, accompanied by a novel method to generate a statistical estimate of the number of unsheltered people in the jurisdiction. First, we develop a power analysis for the sample size of our RDS survey to count unsheltered people experiencing homelessness. Then, we conducted three large-scale population-representative samples in King County, WA (Seattle metro) in 2022, 2023, and 2024. We describe the data collection and the application of our new method, comparing the 2020 PIT count (the last visual PIT count performed in King County) to the new method 2022 and 2024 PIT counts. We conclude with a discussion and future directions.

Evaluation of respondent-driven sampling in seven studies of people who use drugs from rural populations: findings from the Rural Opioid Initiative.

BACKGROUND: Accurate prevalence estimates of drug use and its harms are important to characterize burden and develop interventions to reduce negative health outcomes and disparities. Lack of a sampling frame for marginalized/stigmatized populations, including persons who use drugs (PWUD) in rural settings, makes this challenging. Respondent-driven sampling (RDS) is frequently used to recruit PWUD. However, the validity of RDS-generated population-level prevalence estimates relies on assumptions that should be evaluated. METHODS: RDS was used to recruit PWUD across seven Rural Opioid Initiative studies between 2018-2020. To evaluate RDS assumptions, we computed recruitment homophily and design effects, generated convergence and bottleneck plots, and tested for recruitment and degree differences. We compared sample proportions with three RDS-adjusted estimators (two variations of RDS-I and RDS-II) for five variables of interest (past 30-day use of heroin, fentanyl, and methamphetamine; past 6-month homelessness; and being positive for hepatitis C virus (HCV) antibody) using linear regression with robust confidence intervals. We compared regression estimates for the associations between HCV positive antibody status and (a) heroin use, (b) fentanyl use, and (c) age using RDS-1 and RDS-II probability weights and no weights using logistic and modified Poisson regression and random-effects meta-analyses. RESULTS: Among 2,842 PWUD, median age was 34 years and 43% were female. Most participants (54%) reported opioids as their drug of choice, however regional differences were present (e.g., methamphetamine range: 4-52%). Many recruitment chains were not long enough to achieve sample equilibrium. Recruitment homophily was present for some variables. Differences with respect to recruitment and degree varied across studies. Prevalence estimates varied only slightly with different RDS weighting approaches, most confidence intervals overlapped. Variations in measures of association varied little based on weighting approach. CONCLUSIONS: RDS was a useful recruitment tool for PWUD in rural settings. However, several violations of key RDS assumptions were observed which slightly impacts estimation of proportion although not associations.

Assessing Consistency of Respondent-driven Sampling Estimators by Using Repeated Surveys among People Who Inject Drugs (PWID) in New Jersey.

Respondent-driven sampling (RDS) is widely used to sample populations with higher risk of HIV infection for whom no sampling frames exist. However, few studies have been done to assess the consistency of RDS estimators in real world settings. We conducted an assessment study on the consistency of RDS estimators using data from the National HIV Behavioral Surveillance - People Who Inject Drugs surveys in Newark, New Jersey from 2005 to 2018. Population parameter estimates based on RDS-I, RDS-II, Gile's SS, and HCG were compared longitudinally and cross-sectionally. Population homophily statistics and differential recruitment statistics were estimated and compared. Convergence plots were used for RDS diagnosis. Sensitivity analyses were conducted on population size estimates and seeds biases. By comparing time-insensitive population parameters and population homophily statistics estimated by four RDS estimators, the study found that RDS-II and Gile's SS could provide longitudinally and cross-sectionally consistent estimates and population homophily statistics on gender and sexual orientation. Cross-sectional comparison of time-sensitive population parameter estimates also supported the consistency of RDS-II and Gile's SS. However, RDS-I and HCG did not perform well in those comparisons. In conclusion, RDS estimators may not address all inconsistencies, but RDS-II and Gile's SS are recommended to weight RDS samples given enough consistency was observed in them.

Peer-to-Peer Chain Recruitment for Enrolling Young South African Women into an HIV Pre-exposure Prophylaxis (PrEP) Intervention Study: How Did It Perform?

Peer-to-peer chain recruitment has been used for descriptive studies, but few intervention studies have employed it. We used this method to enroll sexually active women ages 18 to 25 into an online Pre-Exposure Prophylaxis (PrEP) information and motivation intervention pilot in eThekwini (Durban), South Africa. Seeds (N = 16) were recruited by study staff and randomized to Masibambane, Ladies Chat, a Gender-Enhanced group-based WhatsApp Workshop (GE), or Individual-Access (IA), a control condition that provided participants with online information/motivation materials only. Each seed could recruit up to three women to participate in the same study condition, with an incentive for each enrolled woman; participants in subsequent waves could choose to recruit or not. We evaluated if peer-to-peer recruitment was self-sustaining and resulted in enrolling women who, in subsequent waves, had less contact with the health care system and less knowledge about PrEP than the initial seeds. Over three recruitment waves beyond the seeds, 84 women were recruited. Almost 90% of women became recruiters, with each recruiting on average 1.90 women and 1.26 eligible enrolled women. The approach was successful at reaching women with less education but not women with less health system contact and PrEP knowledge across waves. IA participants had a slightly higher, though non-significantly different, percentage of individuals who became Peer Health Advocates (PHAs) than GE participants and, on average, they recruited slightly more women who enrolled. Our findings demonstrated that peer-to-peer recruitment is a feasible and self-sustaining way to recruit SA young women into a PrEP intervention study.

Sleep quality and associated factors among people who inject drugs in Iran: a nationwide survey using respondent-driven sampling.

BACKGROUND: Poor sleep quality is a significant issue among people who inject drugs (PWID). This study aimed to evaluate sleep quality and associated factors among PWID in Iran. METHODS: Using respondent-driven sampling, 2,652 PWID (2,563 male) were recruited in 11 major cities in Iran between 2019 and 2020. The Pittsburgh Sleep Quality Index was utilized to measure sleep quality, and logistic regression was used to assess associations in RDSAnalyst, a software designed for respondent-driven sampling. RESULTS: The overall prevalence of poor sleep quality was 68.4% (68.3% among males and 70.2% among females). Married PWID had higher odds of poor sleep quality (Adjusted Odds Ratio (AOR): 1.41; 95% CI: 1.05, 1.91). Lack of access to sufficient food in the past 12 months was also associated with poor sleep quality (AOR: 1.73; 95% CI: 1.17, 2.57 for sometimes having no access, and AOR: 2.95; 95% CI: 1.93, 4.52 for always having no access compared to always having access). Additionally, good self-rated health was significantly associated with lower odds of poor sleep quality (AOR: 0.19; 95% CI: 0.11, 0.31). CONCLUSION: Poor sleep quality is prevalent among PWID in Iran. It is recommended to mitigate the adverse effects of this issue and enhance the overall quality of life for PWID. Supportive interventions aimed at preventing and treating poor sleep quality, as well as improving overall health outcomes, are essential.

Using Respondent-Driven Sampling (RDS) to Recruit Women With Criminal Legal System-Involvement (CLSI) During the COVID-19 Pandemic.

Recruiting women participants with criminal legal system involvement (CLSI) has always presented challenges, whether gaining access to them in prisons and jails or locating them after release. This research brief describes how the COVID-19 pandemic required us to change our recruitment strategies from previously successful approaches to a hybrid strategy using techniques from respondent-driven sampling (RDS) to recruit CLSI women. The RDS techniques, with internet social media, enabled us to capitalize on the community-based social networks of CLSI women to recruit 255 into our clinical trial of a health education intervention. This new avenue for recruitment can be useful beyond pandemic conditions.

Respondent-Driven Sampling for Estimation of the Cumulative Lifetime Incidence of Abortion in Soweto, Johannesburg, South Africa: A Methodological Assessment.

Respondent-driven sampling (RDS) is a potential strategy for addressing challenges in accurate estimation of abortion incidence, but it relies on often untested assumptions. We conducted an RDS study to estimate the cumulative lifetime incidence of abortion in Soweto, Johannesburg, South Africa (April-December 2018), to evaluate whether RDS assumptions were met, and to compare RDS estimates of incidence with estimates adjusted for employment and age based on census data. A total of 849 participants were recruited from 11 seed participants between April and December 2018. The assumption that individuals can identify target population members and the assumption of approximation of sampling with replacement was met. There were minor violations of the assumptions of seed independence from the final sample and reciprocity of ties. Assumptions of accurate degree reporting and random recruitment were not met. Failure to meet assumptions yielded a study sample with different employment characteristics than those of the target population; this could not be resolved by standard RDS methods. The RDS estimate of cumulative lifetime abortion incidence was 12.1% (95% confidence interval: 9.8, 14.3), and the employment-adjusted estimate was 16.9% (95% confidence interval: 12.8, 22.1). We caution researchers in using RDS for representative estimates of abortion incidence. Use of postsurvey weights to adjust for differences in characteristics between the sample and the target population may yield more representative results.

Innovative Strategies for Remotely Sampling Hard-to-Reach Populations: Assessing Phone Versus Internet Respondent-Driven Sampling Approaches Among Venezuelan Refugees and Migrants in Colombia.

It is challenging to quantitatively measure the health vulnerability and risk factors of refugees and migrants residing outside of formal settlement settings. For hard-to-reach populations without available sampling frames, researchers have increasingly turned to novel sampling and statistical methods, like respondent-driven sampling (RDS). "Standard" RDS is typically conducted face-to-face at fixed sites. However, during the coronavirus disease 2019 (COVID-19) pandemic, face-to-face survey methods and recruitment approaches posed high potential risk of virus transmission and infection, making remote RDS approaches optimal. In this paper, we explore the feasibility of implementing telephone and Internet RDS strategies to assess challenges faced by Venezuelan refugees and migrants in the city of Bogotá, Colombia's capital, and the department of Norte de Santander, the main Venezuelan-Colombian border crossing site. We describe RDS assumptions, survey design, formative research, and the implementation of both strategies and present diagnostics for determining whether assumptions are met. Phone-based recruitment strategies in both locations and the Internet strategy in Bogotá achieved their calculated sample size; however, the Internet strategy in Norte de Santander did not. Most RDS assumptions were sufficiently met at sites where sample sizes were reached. These surveys provide valuable lessons for implementing innovative remote strategies with which to study hard-to-reach populations such as refugees and migrants.

Examining differential success in recruitment using respondent driven sampling (RDS) in a multi-site study of gay, bisexual and other men who have sex with men.

BACKGROUND: The Engage Study is a longitudinal biobehavioral cohort study of gay, bisexual and other men who have sex with men (GBM) in Toronto, Montreal, and Vancouver. Baseline data (2,449 participants) were collected from February 2017 - August 2019 using respondent-driven sampling (RDS). Recruitment in Montreal required fewer seeds, had a much shorter recruitment period, and recruited the largest sample. METHODS: To better understand why RDS recruitment was more successful in Montreal compared to other sites, we conducted an analysis to examine RDS recruitment characteristics for GBM in each of the three study sites, explore demographic characteristics and measures of homophily, that is, the tendency of individuals to recruit other study participants who are like themselves, and compared motivations for study participation. RESULTS: Montreal had the greatest proportion of participants over the age of 45 (29.1% in Montreal, 24.6% in Vancouver, and 21.0% in Toronto) and the highest homophily for this age group, but homophily was high across the three cities. Montreal also reported the lowest percentage of participants with an annual income greater or equal to $60,000 (7.9% in Montreal, 13.1% in Vancouver and 10.6% in Toronto), but homophily was similar across all three cities. The majority of participants indicated interest in sexual health and HIV as the main reason for participating (36.1% in Montreal, 34.7% in Vancouver, and 29.8% in Toronto). Financial interest as the main reason for participation was low (12.7% in Montreal, 10.6% in Vancouver, and 5.7% in Toronto). CONCLUSION: Taken together, although we found some differences in study demographic characteristics and homophily scores, we were unable to fully explain the different recruitment success based on the data available. Our study underlines the fact that success of RDS implementation may vary by unknown factors, and that researchers should be proactive and flexible to account for variability.

Implementation of web-based respondent driven sampling in epidemiological studies.

BACKGROUND: Respondent-driven sampling (RDS) is a peer chain-recruitment method for populations without a sampling frame or that are hard-to-reach. Although RDS is usually done face-to-face, the online version (WebRDS) has drawn a lot of attention as it has many potential benefits, despite this, to date there is no clear framework for its implementation. This article aims to provide guidance for researchers who want to recruit through a WebRDS. METHODS: Description of the development phase: guidance is provided addressing aspects related to the formative research, the design of the questionnaire, the implementation of the coupon system using a free software and the diffusion plan, using as an example a web-based cross-sectional study conducted in Spain between April and June 2022 describing the working conditions and health status of homecare workers for dependent people. RESULTS: The application of the survey: we discuss about the monitoring strategies throughout the recruitment process and potential problems along with proposed solutions. CONCLUSIONS: Under certain conditions, it is possible to obtain a sample with recruitment performance similar to that of other RDS without the need for monetary incentives and using a free access software, considerably reducing costs and allowing its use to be extended to other research groups.

HIV prevalence and associated factors among female sex workers in Iran: a bio-behavioral survey in 2020.

Despite the overall decline in human immunodeficiency virus (HIV) prevalence, it remains unacceptably high in key populations. This study aimed to estimate prevalence of HIV infection and high-risk behaviors among female sex workers (FSWs). This study was a cross-sectional survey of FSWs conducted between December 2019 and August 2020 in eight geographically diverse cities in Iran. After providing informed consent, participants completed a bio-behavioral questionnaire and after completion of the interview, rapid diagnostic tests (RDT) and dried blood spots (DBS) were collected to determine HIV and syphilis status as per national guidelines, if the women consented. All analyzes were based on RDS adjustment. Weighting was done according to Giles'SS estimator. Among the 1515 FSWs, the overall prevalence of HIV and syphilis were 1.6% (95% CI: 0.8-2.3) and zero, respectively. The highest HIV prevalence was observed in Shiraz (5.1%) and Khorramabad city (1.6%). In addition, HIV-positive FSWs had a higher mean age at first sexual contact than HIV-negative FSWs (21.4 ± 5.6 vs. 17.2 ± 4.2 years). Injection drug use and a history of arrest or incarceration were associated with an increased odds of HIV infection (OR = 6.25; 95% CI: 1.90-20.55 and OR = 4.57; 95% CI: 1.64-12.72, respectively). Based on the results, strategies to improve early HIV diagnosis, harm reduction, and use of testing and treatment strategies are needed to reduce and control HIV infections.

Estimating the number of people who inject drugs using repeated respondent-driven sampling (RDS) in a community-based program: implications for the burden of hepatitis C and HIV infections and harm reduction coverage.

Estimates of the population size of people who inject drugs (PWID) are essential for efficient program planning and for monitoring key targets. Existing estimates in Greece are based on the capture-recapture method applied to drug treatment sources. We aimed to obtain estimates based on data collected from a community-based program addressing PWID in Athens, Greece. The program was implemented in 2012-2013 to increase diagnosis and treatment for HIV among PWID during an HIV outbreak. Five Responden-Driven Sampling (RDS) rounds were used to recruit participants. A unique code was used to identify participants among rounds. Capture-recapture was applied to estimate the population size in 2013 (PWID with injection in the past 12 months; active PWID with injection in the past 30 days). Log-linear models were applied. In 2013, the estimated number of active PWID in Athens was 4,117 [95% confidence interval (CI): 3,728-4,507] (vs. 1,956 [95% CI: 1,525-2,565] the existing population size estimate). Based on this estimate, the coverage of needle and syringe programs in 2013 was 103 syringes/PWID/year (vs. 216 based on the existing estimate). The population prevalence of injecting drug use in Athens (past 12 months) was 0.222% (95% CI: 0.200-0.245). The inclusion of data from community-based programs in the estimation of the PWID population size resulted in 2.1-fold higher estimates, compared to the official estimates obtained from drug treatment data, and indicates the need for re-evaluation of necessary resources for harm reduction and elimination of HIV and hepatitis C in PWID.

Awareness of and willingness to use oral HIV self-test kits among Kenyan young adults living in informal urban settlements: a cross-sectional survey.

Self-administered HIV testing may be a promising strategy to improve testing in hard-to-reach young adults, provided they are aware of and willing to use oral HIV self-testing (HIVST). This study examined awareness of and willingness to use oral HIVST among 350 high-risk young adults, aged 18-22, living in Kenya's informal urban settlements. Bivariate and multivariate logistic regressions were used to examine differences in HIVST awareness and willingness by demographic and sexual risk factors. Findings showed that most participants were male (56%) and less than 20 years old (60%). Awareness of oral HIVST was low (19%). However, most participants (75%) were willing to use an oral HIV self-test in the future and ask their sex partner(s) to self-test before having sex (77%). Women (OR = 1.80, 95%CI:1.11, 2.92), older participants (aged 20+) (OR = 2.57, 95% CI:1.48, 4.46), and more educated participants (OR = 2.25, 95%CI:1.36, 3.70) were more willing to use HIVST as compared to men, teen-aged, and less educated participants, respectively. Young adults who reported recent engagement in high-risk sexual behaviors, such as unprotected sex, sex while high or drunk, or sex exchange, were significantly less likely to be willing to use an oral HIV self-test kit (OR = 0.34, 95%CI:0.13,0.86). Those with the highest monthly income (OR = 0.47, 95%CI: 0.25, 0.89) were also less willing to use HIVST. More community- and peer-based efforts are needed to highlight the range of benefits of HIVST (i.e., social, clinical, and structural) to appeal to various youth demographics, in addition to addressing concerns relating to HIVST.

Alarmingly high prevalence of high-risk drug use among palestinian males: a cross-sectional study.

BACKGROUND: The unique socioeconomic context in Palestine, characterized by political and economic tensions, creates conditions that facilitate the spread of illicit drug use among Palestinians. This paper presents findings from a 2017 survey of high-risk drug use (HRDU) among males in four regions in Palestine: the West Bank (north, middle, and south) and the Gaza Strip. These findings are essential for developing effective policies to respond to the increasing use of drugs among Palestinians. METHODS: Eligible participants were males aged 15 years and above who used at least one drug other than non-synthetic hashish or marijuana during the previous week. Participants underwent a face-to-face interview and had their drug use verified by urinalysis. Data were collected using respondent-driven sampling and data were analyzed using the successive sampling estimator. Multivariate regression analysis was conducted to examine factors associated with ever seeking rehabilitation services for illicit drug use in the West Bank and the Gaza Strip. RESULTS: A total of 400 males who use drugs were sampled in Gaza, plus 299 in the south, 300 in the north, and 299 in the middle region of the West Bank. It is estimated that there are 26,500 male HRDUs in Palestine comprising 1.8% of the male population aged 15 and above. Findings indicate that polydrug use is a serious issue in Palestine, especially in the West Bank, and that synthetic marijuana is prevalent among teenagers and young adults. CONCLUSIONS: Palestine must strengthen its national efforts to scale up harm reduction and treatment and care options for people suffering from drug use disorders, especially those involved in polydrug use. Additional measures are needed to prevent substance use among children and youth, support the families of people who use drugs, and ensure the continuity of HRDU services during emergencies.

Relationship between drinking risk and preferences for helping resources among emerging adults living in disadvantaged communities in the Southeastern United States.

Compared to campus-based alcohol interventions for college students, services for emerging adult (EA) risky drinkers who reside off-campus in disadvantaged communities are not well established. This web survey assessed drinking practices, problems, and preferences for professional and lay helping resources spanning digital and in-person formats among community-dwelling EAs to guide services for them and determine whether drinking risk levels varied by preferences for help. Digital respondent-driven sampling recruited EA risky drinkers from disadvantaged communities (N = 356; M age = 23.6 years, 64.0% women, 77.4% employed, 64.9% residing in impoverished areas above the US average, 53.5% income < $20k/year). A web survey assessed participants' drinking practices and problems, including alcohol use disorder symptoms, and help-seeking preferences for smartphone apps; online help; in-person help from doctors, clinics, teachers, and school programs; mutual help groups; and help from friends and family. Preferences were related to participant drinking risks using generalized linear modeling. Modeling results showed that risk levels were related to help-seeking preferences. EAs reporting more negative consequences preferred smartphone apps and help from friends, whereas EAs reporting fewer negative consequences and drinking days preferred professional in-person help (Ps < 0.05). Although >90% fulfilled alcohol use disorder diagnostic criteria, <4% had received an alcohol-related intervention. EAs who are riskier drinkers appear less likely to use professional resources in favor of informal and online resources that allow greater anonymity. Findings can guide services for this underserved population that are responsive to drinker risk levels.

HIV prevalence and associated risk factors among young tertiary student men who have sex with men (MSM) in Nairobi, Kenya: a respondent-driven sampling survey.

BACKGROUND: Young men who have sex with men (MSM), are a key population at higher risk of HIV infection yet they are underrepresented in research. We conducted a bio-behavioral survey to estimate HIV prevalence and associated risk factors among tertiary student MSM (TSMSM) in Nairobi, Kenya. METHODS: Between February and March 2021, 248 TSMSM aged ≥ 18 years who reported sex with another man in the past year participated in a respondent-driven sampling (RDS) based cross-sectional survey. Participants completed an electronically self-administered behavioral survey and provided a blood sample for HIV antibody testing, alongside urine, anorectal and oropharyngeal swabs for pooled testing of sexually transmitted infections using a multiplex nucleic acid amplification test. RDS-Analyst v.0.72 and Stata v.15 software were used for data analysis. Differences in proportions were examined using chi-square (χ2) test, and unweighted multivariate logistic regression was used to assess factors associated with HIV infection. RESULTS: HIV prevalence among study participants was 8.3%, whereas the weighted prevalence was 3.6% (95% CI: 1.3-6.0%). Median ages of participants, and at self-reported first anal sex with a man were 21(interquartile range [IQR] 20-22) and 18 (IQR 17-19) years, respectively. A majority (89.3%) of TSMSM owned a smart phone, 46.5% had ever used a geosocial networking app for MSM such as Grindr ® to find a sex partner, and a third (33.6%) met their last sex partner online.  Almost three-quarters (71.3%) had > 1 male sex partner in the year before the survey. A third (34.3%) did not use condoms with their last sex partner, 21.2% received money from their last sex partner and 40.9% had taken alcohol/another drug during their last sexual encounter. HIV infection was associated with studying in private institutions (adjusted odds ratio[AOR] = 6.0; 95% confidence intervals [CI] : 1.2-30.0, p = 0.027), preferring a sex partner of any age-younger, same or older (AOR = 5.2; 95 CI: 1.1-25.2, p = 0.041), last sex partner being > 25 years (AOR = 6.4; 95% CI: 1.2-34.6, p = 0.030), meeting the last sex partner online (AOR = 4.2; 95% CI; 1.1-17.0, p = 0.043) and testing positive for Neisseria gonorrhea (AOR = 7.8; 95% CI: 2.0-29.9, p = 0.003). CONCLUSIONS: HIV prevalence among TSMSM in Nairobi is alarmingly high, demonstrating a need for tailored prevention and control interventions for this young key population.

Mobility and HIV vulnerabilities among female sex workers in Guinea-Bissau: findings from an integrated bio-behavioral survey.

BACKGROUND: Mobility is an important risk determinant for HIV given the potential for intermittent access to HIV services. Mobility may be particularly relevant among female sex workers, (FSW) who have been shown to be at high risk for HIV in settings around the world. Data regarding the role mobility plays in exacerbating HIV risks among FSW across Sub-Saharan Africa remains limited, and data on FSW in Guinea-Bissau is sparse. METHODS: FSW in four regions of Guinea-Bissau were recruited with a respondent-driven sampling (RDS) method and participated in an integrated bio-behavioral survey between September 27, 2017 and January 26, 2018. Associations between reported general mobility, mobility to or residence in Bissau, and social and HIV vulnerabilities among FSW in Guinea-Bissau were assessed using multivariable logistic regression models. Population proportions were weighted for RDS sampling, while logistic regression models were not. RESULTS: Survey respondents included 323 individuals in Bissau, 45 in Bissorã, 140 in Bafatá, and 59 in Gabu. Statistical analyses demonstrated that mobility to more than one destination was significantly associated with recent sex without a condom (ie, sex without a condom within the last three sex acts) with both clients (aOR: 2.47 (95% CI: 1.08, 5.64)) and non-paying partners (aOR: 5.39 (95% CI: 2.61, 11.15)) compared to non-mobility. However, mobility to one or more locations was also associated with higher odds of receiving HIV prevention information, and mobility to more than one location was associated with participating in programming with HIV-related organizations. CONCLUSIONS: These results suggest that while some prevention services including HIV prevention information reach mobile FSW in Guinea-Bissau more than their non-mobile counterparts, the higher rates of condomless sex among mobile FSW suggest that HIV prevention needs may remain unmet for mobile FSW in Guinea-Bissau. Additionally, the results suggest a nuanced relationship between mobility, place of residence, and HIV and social vulnerabilities and prevention indicators.

Trends and Factors Affecting Knowledge of and Stigma and Violence Towards Female Sex Workers in Morocco.

BACKGROUND: We investigate factors affecting HIV knowledge, stigma, and violence among female sex workers (FSW) in Agadir, Rabat, Fes, and Tangier, Morocco, over three rounds of HIV surveillance surveys (2012, 2016, and 2019) conducted using respondent-driven sampling (RDS). Multivariable analyses from RDS studies examining the relationships between variables are under-utilized, particularly analyses that combine multiple locations and years of data together in a principled manner. METHOD: We fit three weighted logistic regression models for HIV transmission knowledge, having been denied service (experienced stigma), and having been hit (experienced violence) in the last 12 months, and perform model selection using 41 possible explanatory variables. RESULTS: Variables significantly associated with higher risk included reasons for sex work, how FSW solicit clients, if female family members are also involved in sex work, ever being forced to have sex, and ever being arrested or jailed. There were also significant differences between cities and in trends over time, with HIV transmission knowledge increasing and having been denied health services and having been hit decreasing. CONCLUSION: We found associations indicating that some particularly vulnerable FSW may be subject to multiple intersecting risks related to HIV knowledge, stigma, and violence which may decrease their agency to receive proper HIV testing, care, and treatment. Although Morocco has made excellent progress in providing HIV services to vulnerable populations, this additional analysis will be useful as Morocco makes programmatic decisions related to ending HIV by 2030.

Gay App Use, Sexuality Traits, and High-Risk Sexual Behaviors Among Men Who Have Sex With Men in China: Mediation Analysis.

BACKGROUND: Gay geosocial networking apps, also known as "gay apps," have gained increasing popularity in the men who have sex with men (MSM) community. Certain sexuality traits and gay app use are both associated with high-risk sexual behaviors among MSM. However, little is known about the underlying mechanism of such relationships. OBJECTIVE: Based on the uses and gratifications theory, this study aimed to test the mediation effect of gay app use on the relationship between sexuality traits (sexual compulsivity and sexual sensation seeking) and high-risk sexual behaviors (multiple sexual partners and unprotected anal intercourse) among MSM. METHODS: A cross-sectional, multicenter study was conducted in Wuhan and Changsha, China, from August to October 2020. A representative sample of 402 MSM was recruited through respondent-driven sampling. A self-administered web-based structured questionnaire was used to collect data on sociodemographic information, high-risk sexual behaviors, gay app use, sexual compulsivity, and sexual sensation seeking. Path analysis was conducted to assess the mediation effect. RESULTS: Our study revealed that 67.42% (n=271) of MSM used gay apps for seeking potential sexual partners, with 37.06% (n=149) of them engaging in unprotected anal intercourse, and 45.42% (n=218) of them having multiple sexual partners. Of the participants, 17.16% (n=69) reported significant sexual compulsivity, while 29.10% (n=117) reported significant sexual sensation seeking. Notably, gay app usage partially mediated the relationship between sexual compulsivity and multiple sexual partners but fully mediated the relationship between sexual compulsivity and unprotected anal intercourse. Furthermore, gay app usage partially mediated the relationship between sexual sensation seeking and multiple sexual partners but fully mediated the relationship between sexual sensation seeking and unprotected anal intercourse. CONCLUSIONS: High-risk sexual behaviors are common among MSM. Most MSM rely on gay apps to find sexual partners, which, when combined with higher levels of sexual compulsivity and sexual sensation seeking, can increase the likelihood of engaging in high-risk sexual behaviors. Therefore, interventions aimed at reducing these behaviors among MSM should focus on addressing the use of gay apps, while also considering the influence of their sexuality traits on gay app use.

Design and implementation of a web-based, respondent-driven sampling solution.

BACKGROUND: Respondent-driven sampling (RDS) refers both to a chain-referral sampling method and an analytical model for analysing sampled data. Web-based respondent-driven sampling (webRDS) uses internet-based recruitment coupled with an electronic survey to carry out RDS studies; there is currently no commercially available webRDS solution. We designed and developed a webRDS solution to support a research study aimed at estimating conflict-attributable mortality in Yemen. Our webRDS solution is composed of an existing survey platform (i.e. ODK) and a bespoke RDS system. The RDS system is designed to administer and manage an RDS survey cascade and includes: (1) an application programming interface, (2) a study participant client, and (3) an administrator interface. We report here on the design of the webRDS solution and its implementation. RESULTS: We consulted members of the Yemeni diaspora throughout the development of the solution. Technical obstacles were largely the result of: WhatsApp's policies on bulk messaging and automated messaging behaviour, the inherent constraints of SMS messaging, and SMS filtering behaviour. Language support was straight-forward yet time consuming. Survey uptake was lower than expected. Factors which may have impacted uptake include: our use of consumable survey links, low interest amongst the diaspora population, lack of material incentives, and the length and subject matter of the survey itself. The SMS/WhatsApp messaging integration was relatively complex and limited the information we could send potential participants. CONCLUSION: Despite lower-than expected survey uptake we believe our webRDS solution provides efficient and flexible means to survey a globally diverse population.