Deep learning and social network analysis elucidate drivers of HIV transmission in a high-incidence cohort of people who inject drugs

Network-based strategies to combat HCV: Examining social and spatial drivers of transmission among PWID in New Delhi

People who inject drugs (PWID) account for some of the fastest-growing HCV epidemics globally. While individual risk factors for infection are understood, less is known about network and spatial factors critical for elimination strategies. Two thousand five hundred twelve PWID in New Delhi, India, were recruited (2017-19) through network referrals. Biometrics identified duplicates and cross-network linkages. Participants completed semi-annual surveys and blood tests for HCV antibodies and RNA. Poisson regression and network analyses identified predictors of incident HCV and compared network-based intervention approaches. Baseline HCV antibody prevalence was 65.1%, of whom 79.6% were HCV RNA-positive. We observed 92 HCV seroconversions over 382.25 person-years (incidence: 24.1 per 100 person-years). Of the 92 seroconverters, 67% (62) were directly connected to an RNA-positive participant, and all were within one degree of separation from an RNA-positive participant. Individual-level factors associated with seroconversion included age, sexual activity, and injection behaviours. After adjusting for individual-level factors, seroconversion was significantly associated with number of RNA-positive partners (adjusted incidence rate ratio [AIRR] = 1.30) and injecting at a particular venue (AIRR = 2.53). This association extended to indirect ties, with 17% reduced odds of seroconversion for each degree of separation from the venue (AIRR = 0.83). Network analyses comparing intervention strategies found that targeting venues identified more cases compared to a treat-a-friend approach. We observed a fast-growing HCV epidemic driven by viremia within individuals' immediate networks and indirect social and spatial ties, demonstrating the importance of achieving broad, sustained virologic response and rethinking network-based interventions to include venues.

Differential Burden of HIV Among Adolescent Girls and Young Women by Places Associated With Sex Work: An Observational Study in Mombasa, Kenya

BACKGROUND

The design of HIV prevention programs for adolescent girls and young women (AGYW) are informed by data on who is at highest risk and where they can be reached. Places (hotspots) associated with selling sex are an established outreach strategy for sex work (SW) programs but could be used to reach other AGYW at high risk.

SETTING

This study took place in Mombasa, Kenya.

METHODS

We conducted a cross-sectional, bio-behavioural survey among (N = 1193) sexually active AGYW aged 14-24 years recruited at hotspots. We compared HIV prevalence by subgroup (SW; transactional sex, TS; and non-transactional sex), stratified by hotspot type (venues and nonvenues). We examined whether associations between HIV prevalence and hotspot/subgroup remained after adjustment for individual-level risk factors, and estimated HIV prevalence ratio with and without adjustment for these individual-level factors.

RESULTS

Overall HIV prevalence was 5.6%, 5.3% in venues and 7.3% in nonvenues. Overall SW HIV prevalence was 2-fold higher than among participants engaged in nontransactional sex. After adjusting for age and individual-level risk factors, HIV prevalence was 2.72 times higher among venue-based SWs (95% confidence interval: 1.56 to 4.85) and 2.11 times higher among nonvenue AGYW not engaged in SW (95% confidence interval: 0.97 to 4.30) compared with venue-based AGYW not engaged in SW.

CONCLUSION

AGYW who sell sex remain at high risk of HIV across types of hotspots. The residual pattern of elevated HIV burden by AGWY subgroup and hotspot type suggests that unmeasured, network-level factors underscore differential risks. As such, hotspots constitute a "place" to reach AGYW at high risk of HIV.

Injection network drivers of HIV prevention service utilization among people who inject drugs: results of a community-based sociometric network cohort in New Delhi, India

INTRODUCTION

Injection drug networks may influence their network members' health-seeking behaviours. Using data from a sociometric injecting partner network of people who inject drugs (PWID) in New Delhi, India, we assessed the role of injecting partner (alter) behaviours on individual engagement in HIV prevention services.

METHODS

We enumerated injecting partner linkages among 2512 PWID using coupon referrals and biometric data from November 2017 to March 2020. Participants completed interviewer-administered questionnaires and provided information on injection behaviours, injecting partners, HIV/hepatitis C (HCV) testing and service engagement. Multilevel multiple-membership models (MMMM) evaluated individual PWID HIV testing, medication for opioid use disorder (MOUD) and syringe service engagement as a function of alter attributes, accounting for membership across multiple ego-networks. Logistic regression models assessed parallel associations among socially proximal injecting peers, defined as PWID ≤3 path length from ego.

RESULTS

Median age was 26 years; 99% were male. PWID had median 2 injecting partners and 8 socially proximal peers; 14% reported HIV testing, 33% accessed MOUD and 13% used syringe services 6 months prior. In MMMM analyses, PWID with ≥1 versus 0 injecting partners who received HIV testing were significantly more likely to report HIV testing (adjusted odds ratio [aOR]: 2.27, 95% confidence interval [CI]: 1.68-3.16), MOUD (aOR: 1.99, 95% CI: 1.60-2.53) and syringe service use (aOR: 1.66, 95% CI: 1.21-2.39). We observed similar findings for individual MOUD and syringe service use. Having ≥1 versus 0 HIV-positive partners was associated with decreased HIV testing and MOUD but increased syringe service use (aOR: 1.54, 95% CI: 1.09-2.17). PWID with ≥1 versus 0 socially proximal peers who used non-sterile injection equipment reported increased HIV testing (aOR: 1.39, 95% CI: 1.01-1.92), MOUD (aOR: 1.40, 95% CI: 1.10-1.77) and syringe service use (aOR: 1.82, 95% CI: 1.23-2.68).

CONCLUSIONS

We found differential associative relationships between individual HIV prevention service engagement and the health or risk behaviours of direct and indirect alters. Characterizing network exposure beyond direct injecting partnerships provided important context on possible mechanisms of behavioural influence. Findings could be leveraged to design peer-based interventions that promote network diffusion of health-seeking behaviours.

Network centrality and HIV prevention service use among people who inject drugs: Findings from a sociometric network cohort in New Delhi, India

BACKGROUND AND AIMS

Network centrality, an indicator of an individual's importance and potential to drive behavioral change, is rarely used to select peer educators. Individual-level predictors of network centrality might be useful to identify people who inject drugs (PWID) for potential roles as peer navigators or change agents in network-based interventions in settings where sociometric data are unavailable. We assessed the relationship between network centrality and HIV prevention service engagement to determine whether centrally-positioned PWID share measurable commonalities.

DESIGN

Observational study and survey using baseline data from a sociometric network cohort of PWID, enumerated using network software and biometric data (2017-2020). Network ties corresponded to direct injection partnerships in the prior month.

SETTING

New Delhi, India.

PARTICIPANTS

A total of 2512 PWID who were ≥18 years, provided written informed consent, and reported illicit injection drug use within the 24 months before study enrollment.

MEASUREMENTS

Interviewer-administered questionnaires measured demographics and substance use behaviors. Central versus peripheral network position was categorized using betweenness centrality 75th%ile . Logistic regression was used to estimate adjusted odds ratios (aOR) with 95% confidence intervals (95%CI) between network position and HIV testing, medication for opioid use disorder (MOUD), or syringe service use. Lasso models selected predictors of central network position among 20 covariates detailing demographic, biologic, and substance use information. Predictive accuracy was evaluated using model performance metrics.

FINDINGS

Overall, median age was 26 years (interquartile range 22-34); 99% were male; 628 were classified as central. Compared with PWID at the periphery, central PWID were more likely to use MOUD (aOR: 1.59, 95%CI: 1.30-1.94) and syringe services (aOR: 2.91, 95%CI: 2.25, 3.76) in the prior six months. Findings for HIV testing were inconclusive (aOR: 1.30, 95%CI: 1.00-1.69). The lasso variable selector identified several predictors of network centrality: HIV and hepatitis C infection, number of PWID seen in the prior month, injecting heroin and buprenorphine (vs. heroin only) six months prior, sharing injection equipment six months prior, experiencing drug overdose in the past year, and moderate/severe depression (vs. none/mild). Average agreement between model-predicted vs. observed values was 0.75; area under the receiver operator curve was 0.69.

CONCLUSIONS

In a socioeconomic network of people who inject drugs (PWID) in New Delhi, India, there are common characteristics among individuals based on their network position (central vs. peripheral) but individual-level predictors have only moderate predictive accuracy. Although central network members appear to be more likely to use HIV prevention services than peripheral network members, their potential as change agents may be limited by other factors that impede their ability to adopt or promote HIV prevention service use.

Social networks, secondary syringe exchange, and opioid agonist therapy retention among people who inject drugs in Hartford, CT

BACKGROUND

Opioid agonist therapies (OAT) and  harm reduction such as syringe service programs (SSP) have been shown to be effective in preventing adverse outcomes such as overdose deaths, HIV and Hepatitis C infections among people who inject drugs (PWID). The importance of social network influence on disease transmission is well established, yet the interplay between harm reduction and network structures is, generally, not well understood. This study aims to analyze how social networks can mediate the harm reduction effects associated with secondary exchange through syringe service programs (SSP) and opioid agonist therapies (OAT) among injection network members.

METHODS

Sociometric data on networks on people who inject drugs from Hartford, CT, which were collected in 2012-2013, provided assessment of risk behaviors among 1574 injection network members, including participation in OAT and SSP. Subject's network characteristics were examined in relation to retention in OAT, as well as secondary syringe exchange using exponential random graph model (ERGM) and regression.

RESULTS

Based on the analysis, we found that probability of individuals being retained in OAT was positively associated with the OAT retention status of their peers within the network. Using simulations, we found that higher levels of positive correlation of OAT retention among network members can result in reduced risk of transmission of HIV to network partners on OAT. In addition, we found that secondary syringe exchange engagement was associated with higher probability of sharing of paraphernalia and unsterile needles at the network level.

CONCLUSIONS

Understanding how networks mediate risk behaviors is crucial for making progress toward ending the HIV epidemic.

Incidence of HIV and hepatitis C virus among people who inject drugs, and associations with age and sex or gender: a global systematic review and meta-analysis

BACKGROUND

Measuring the incidence of HIV and hepatitis C virus (HCV) infection among people who inject drugs (PWID) is key to track progress towards elimination. We aimed to summarise global data on HIV and primary HCV incidence among PWID and associations with age and sex or gender.

METHODS

In this systematic review and meta-analysis, we updated an existing database of HIV and HCV incidence studies among PWID by searching MEDLINE, Embase, and PsycINFO, capturing studies published between Jan 1, 2000, and Dec 12, 2022, with no language or study design restrictions. We contacted authors of identified studies for unpublished or updated data. We included studies that estimated incidence by longitudinally re-testing people at risk of infection or by using assays for recent infection. We pooled incidence and relative risk (RR; young [generally defined as ≤25 years] vs older PWID; women vs men) estimates using random-effects meta-analysis and assessed risk of bias with a modified Newcastle-Ottawa scale. This study is registered with PROSPERO, CRD42020220884.

FINDINGS

Our updated search identified 9493 publications, of which 211 were eligible for full-text review. An additional 377 full-text records from our existing database and five records identified through cross-referencing were assessed. Including 28 unpublished records, 125 records met the inclusion criteria. We identified 64 estimates of HIV incidence (30 from high-income countries [HICs] and 34 from low-income or middle-income countries [LMICs]) and 66 estimates of HCV incidence (52 from HICs and 14 from LMICs). 41 (64%) of 64 HIV and 42 (64%) of 66 HCV estimates were from single cities rather than being multi-city or nationwide. Estimates were measured over 1987-2021 for HIV and 1992-2021 for HCV. Pooled HIV incidence was 1·7 per 100 person-years (95% CI 1·3-2·3; I2=98·4%) and pooled HCV incidence was 12·1 per 100 person-years (10·0-14·6; I2=97·2%). Young PWID had a greater risk of HIV (RR 1·5, 95% CI 1·2-1·8; I2=66·9%) and HCV (1·5, 1·3-1·8; I2=70·6%) acquisition than older PWID. Women had a greater risk of HIV (RR 1·4, 95% CI 1·1-1·6; I2=55·3%) and HCV (1·2, 1·1-1·3; I2=43·3%) acquisition than men. For both HIV and HCV, the median risk-of-bias score was 6 (IQR 6-7), indicating moderate risk.

INTERPRETATION

Although sparse, available HIV and HCV incidence estimates offer insights into global levels of HIV and HCV transmission among PWID. Intensified efforts are needed to keep track of the HIV and HCV epidemics among PWID and to expand access to age-appropriate and gender-appropriate prevention services that serve young PWID and women who inject drugs.

FUNDING

Canadian Institutes of Health Research, Fonds de recherche du Québec-Santé, Canadian Network on Hepatitis C, UK National Institute for Health and Care Research, and WHO.

FAD: Fine-Grained Adversarial Detection by Perturbation Intensity Classification

Adversarial examples present a severe threat to deep neural networks' application in safetycritical domains such as autonomous driving. Although there are numerous defensive solutions, they all have some flaws, such as the fact that they can only defend against adversarial attacks with a limited range of adversarial intensities. Therefore, there is a need for a detection method that can distinguish the adversarial intensity in a fine-grained manner so that subsequent tasks can perform different defense processing against perturbations of various intensities. Based on thefact that adversarial attack samples of different intensities are significantly different in the highfrequency region, this paper proposes a method to amplify the high-frequency component of the image and input it into the deep neural network based on the residual block structure. To our best knowledge, the proposed method is the first to classify adversarial intensities at a fine-grained level, thus providing an attack detection component for a general AI firewall. Experimental results show that our proposed method not only has advanced performance in AutoAttack detection by perturbation intensity classification, but also can effectively apply to detect examples of unseen adversarial attack methods.