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BACKGROUND HIV testing is the cornerstone of strategies for achieving the fast-track target to end the AIDS epidemic by 2030. Self-testing has been proven to be an effective health intervention for men who have sex with men (MSM). While social network–based approaches for distributing HIV self-tests are recommended by the World Health Organization, their implementation consists of multiple steps that need to be properly evaluated. OBJECTIVE This study aimed to assess the implementation cascade of a social network–based HIV self-test approach for reaching MSM who had never undergone testing in Hong Kong. METHODS This is a cross-sectional study. Seed MSM participants were recruited through different web-based channels, who in turn invited their peers to participate in this study. A web-based platform was set up to support the recruitment and referral process. Participants could request for an oral fluid or a finger-prick HIV self-test, with or without real-time support, after completing a self-administered questionnaire. Referrals could be made upon uploading the test result and passing the web-based training. Characteristics of participants completing each of these steps and their preferences for the type of HIV self-test were evaluated. RESULTS A total of 463 MSM were recruited, including 150 seeds. Participants recruited by seeds were less likely to have previously been tested for HIV (odds ratio [OR] 1.80, 95% CI 1.06-3.04, P=.03) and have lower confidence in performing self-tests (OR 0.66, 95% CI 0.45-0.99, P=.045). Almost all (434/442, 98%) MSM who completed the questionnaire requested a self-test, of whom 82% (354/434) had uploaded their test results. Participants requesting support were new to self-testing (OR 3.65, 95% CI 2.10-6.35, PPP=.02), especially through location-based networking apps (OR 2.13, 95% CI 1.31-3.49, P=.002). They also gave higher usability scores along the implementation cascade (median 81 vs 75, P=.003). CONCLUSIONS The social network approach was effective in diffusing HIV self-tests in the MSM community and reaching nontesters. Support and option to choose a preferable type of self-test are essential to address users’ individual needs when delivering HIV self-tests. A positive user experience throughout the processes along the implementation cascade is vital to transform a tester into a promoter. CLINICALTRIAL ClinicalTrials.gov NCT04379206; https://clinicaltrials.gov/ct2/show/NCT04379206

Objective Contact tracing of reported infections could enable close contacts to be identified, tested, and quarantined for controlling further spread. This strategy has been well demonstrated in the surveillance and control of COVID-19 (coronavirus disease 2019) epidemics. This study aims to leverage contact tracing data to investigate the degree of spread and the formation of transmission cascades composing of multiple clusters. Materials and Methods An algorithm on mining relationships between clusters for network analysis is proposed with 3 steps: horizontal edge creation, vertical edge consolidation, and graph reduction. The constructed network was then analyzed with information diffusion metrics and exponential-family random graph modeling. With categorization of clusters by exposure setting, the metrics were compared among cascades to identify associations between exposure settings and their network positions within the cascade using Mann-Whitney U test. Results Experimental results illustrated that transmission cascades containing or seeded by daily activity clusters spread faster while those containing social activity clusters propagated farther. Cascades involving work or study environments consisted of more clusters, which had a higher transmission range and scale. Social activity clusters were more likely to be connected, whereas both residence and healthcare clusters did not preferentially link to clusters belonging to the same exposure setting. Conclusions The proposed algorithm could contribute to in-depth epidemiologic investigation of infectious disease transmission to support targeted nonpharmaceutical intervention policies for COVID-19 epidemic control.

Molecular surveillance of infections is essential in monitoring their transmission in the population. In this study, newly diagnosed HIV patients' phylogenetic, clinical and behavioural data were integrated, and an information diffusion model was incorporated in analysing transmission dynamics. A genetic network was constructed from HIV sequences, from which transmission cascades were extracted. From the transmission cascades, CRF01_AE had higher values of information diffusion metrics, including scale, speed and range, than that of B, signifying the distinct transmission patterns of two circulating subtypes in Hong Kong. Patients connected in the network, were more likely male, younger, of main circulating subtypes, to have acquired HIV infection locally, and a higher CD4 level at diagnosis. Genetic connections varied among men who have sex with men (MSM) who used different channels of sex networking and varied in their engagement in risk behaviours. MSM using recreational drugs for sex held positions of greater importance within the network. Significant differences in network metrics were observed among MSM as differentiated by their mobile apps usage patterns, evidencing the impact of social network on transmission networks. The applied model in the presence of consistently collected longitudinal data could enhance HIV molecular epidemiologic surveillance for informing future intervention planning.

Background Pre-exposure prophylaxis (PrEP) is an effective means of HIV prevention for men who have sex with men (MSM), a key population whose engagement is crucial for achieving effective public health outcomes. An optimal service model would be important in planning the implementation of PrEP in places where such service has not been established. Methods A qualitative study was conducted to delineate the attributes of an optimal PrEP service model for MSM in Hong Kong, a city where no formal PrEP programs existed. Twenty purposively sampled MSM who were enrollees of two pilot PrEP projects participated in the semi-structured interviews promoting story-telling. The coded data were thematically analyzed following Grounded Theory approach, focusing on uncovering a typology of the essential attributes of an optimal PrEP service model, and the reasons for such preferences. Results Participating MSM were all ethnic Chinese and aged 26 to 52 years. All had received PrEP from pilot projects in conjunction with periodic screening of sexually transmitted infections (STI), HIV antibody, and plasma creatinine. Four major themes emerged as regards the attributes of a preferred PrEP service: (i) comprehensiveness of HIV/STI and safety monitoring; (ii) convenient unitary service; (iii) stigma-free PrEP access and protecting confidentiality; and (iv) affordable price. Whereas regular provision of PrEP was acceptable to MSM, unaffordability and related stigma were the anticipated challenges for potential service providers. Conclusions The qualitative assessment of MSM’s preference for PrEP service delivery has yielded important information on the many facets of a desirable service model.

Exposure setting is crucial in the formation and propagation of SARS-CoV-2 transmission clusters. In this cohort study, transmission networks of 2 waves were differentiated by exposure setting using territory-wide surveillance data with clinical and laboratory records in Hong Kong. Characteristically, the first wave had resulted from imported cases followed by local transmissions, while the second wave was constituted primarily by local infections. With a 4-fold higher caseload, the second wave featured predominance of epidemiologically linked, local, older and asymptomatic patients with higher viral loads and shorter inpatient days. The 1028 transmission clusters formed 155 cascades composing at least two clusters. Daily and social activities were exposure settings that bridged clusters while residences usually terminated transmission cascades. Regulatory restrictions on social activities extinguished cluster formation in bars, but shifted to private parties in the second wave. The results confirmed that strategic interventions targeting exposure settings could achieve effective epidemic control.

BACKGROUND Digital interventions have been applied for promoting HIV prevention and care among men who have sex with men (MSM). As user interface (UI) design plays a role in determining usability and user experience (UX), the intervention outcome could be affected. OBJECTIVE In this study, we hypothesized that 2 UI design styles, namely gamification and neumorphism, could impact usability and be differentially preferred by distinct groups of MSM. METHODS A prospective parallel-group open-label randomized controlled trial was conducted in Hong Kong. Eligible participants were adult MSM recruited by the research team or referred by enrolled participants, who followed instructions for performing an HIV self-test and promoted its use within their social network. Participants were randomized in a 1:1 ratio into either a gamification or neumorphism arm, with primarily visual differences in the UI only. The primary outcome was usability measured by the System Usability Scale (SUS) between the 2 arms. Distinct characteristics of promoters in the 2 arms who gave an SUS score of 80 or above were identified. RESULTS Of 463 MSM registered in the study, 232 and 231 were randomized to the gamification and neumorphism arms, respectively. Excluding those who did not request a self-test kit, data from 218 and 216 participants in the gamification and neumorphism arms, respectively, were analyzed (totally 434 participants). With a median SUS score of 80 overall, participants in the neumorphism arm gave a higher score (PP=.002). Promoters used social media for sex networking (P=.02), used pre-exposure prophylaxis in the preceding year (P=.006), had higher satisfaction in UI design (PP=.04). In general, higher usability was recorded among participants who were confident in performing the HIV self-test (PP=.01), preferred a specific partner body image type (P=.03), and progressed toward peer referral by completing online training (P=.04). CONCLUSIONS Both gamified and neumorphic UI designs were well-accepted by MSM. UX and satisfaction of UI were both crucial in influencing the willingness of MSM to promote the application by referring their peers in the community to participate. The simplistic visual design of neumorphism conferred a more general acceptance in the community, whereas gamification was preferred in certain MSM subcommunities. Appropriate UI/UX design should be considered when developing digital interventions targeting the MSM community. CLINICALTRIAL ClinicalTrials.gov NCT04379206; https://clinicaltrials.gov/ct2/show/NCT04379206

Background Digital interventions have been applied for promoting HIV prevention and care among men who have sex with men (MSM). As user interface (UI) design plays a role in determining usability and user experience (UX), the intervention outcome could be affected. Objective In this study, we hypothesized that 2 UI design styles, namely gamification and neumorphism, could impact usability and be differentially preferred by distinct groups of MSM. Methods A prospective parallel-group open-label randomized controlled trial was conducted in Hong Kong. Eligible participants were adult MSM recruited by the research team or referred by enrolled participants, who followed instructions for performing an HIV self-test and promoted its use within their social network. Participants were randomized in a 1:1 ratio into either a gamification or neumorphism arm, with primarily visual differences in the UI only. The primary outcome was usability measured by the System Usability Scale (SUS) between the 2 arms. Distinct characteristics of promoters in the 2 arms who gave an SUS score of 80 or above were identified. Results Of 463 MSM registered in the study, 232 and 231 were randomized to the gamification and neumorphism arms, respectively. Excluding those who did not request a self-test kit, data from 218 and 216 participants in the gamification and neumorphism arms, respectively, were analyzed (totally 434 participants). With a median SUS score of 80 overall, participants in the neumorphism arm gave a higher score (P Conclusions Both gamified and neumorphic UI designs were well-accepted by MSM. UX and satisfaction of UI were both crucial in influencing the willingness of MSM to promote the application by referring their peers in the community to participate. The simplistic visual design of neumorphism conferred a more general acceptance in the community, whereas gamification was preferred in certain MSM subcommunities. Appropriate UI/UX design should be considered when developing digital interventions targeting the MSM community. Trial Registration ClinicalTrials.gov NCT04379206; https://clinicaltrials.gov/ct2/show/NCT04379206

Introduction Both daily and on‐demand regimens have been proven effective for pre‐exposure prophylaxis (PrEP) against HIV in men who have sex with men (MSM). We aimed to compare the two regimens on their coverage of condomless anal intercourse (CLAI) in MSM. Methods A randomized, controlled, open‐label, crossover trial was conducted in a teaching hospital in Hong Kong. Participants were sexually active HIV‐negative MSM aged 18 years or above with normal renal function and without chronic hepatitis B infection. Oral tenofovir disoproxil fumarate 300 mg/emtricitabine 200 mg (TDF/FTC) tablets were prescribed for PrEP. After a 2‐week lead‐in with daily TDF/FTC for treatment‐naïve MSM for tolerance assessment, participants were randomly assigned in a 1:1 ratio with a block size of four to either daily‐first or on‐demand‐first arm based on the IPERGAY study, for receiving PrEP for 16 weeks, then crossed‐over to the alternative regimen for another 16 weeks. The primary outcome was the proportion of days with PrEP‐covered CLAI by intention‐to‐treat analysis. The trial is registered with the CCRB Clinical Trials Registry, CUHK, CUHK_CCRB00606, and is closed to accrual. Results Between 25 August 2018 and 23 March 2019, 119 eligible participants were assigned to daily‐first arm (n = 59) and on‐demand‐first arm (n = 60) with an 87% overall completion rate (n = 103). With 96% and 54% of days on PrEP during daily and on‐demand periods, respectively, the proportion of days with PrEP‐covered CLAI between two arms were not statistically different (92% vs. 92%, p = 0.93). About half (47%) were diagnosed with at least one episode of incident sexually transmitted infection. Mild and time‐limited adverse events, including diarrhoea, headache, nausea and dizziness, were reported in 37 (31%) and 10 (8%) during the daily and on‐demand periods, respectively. At the end of the study, a similar proportion favoured daily or on‐demand regimen. Conclusions High prevention‐effective adherence, as reflected from the coverage of CLAI, was achievable by either daily or on‐demand PrEP among MSM, albeit a higher number of tablets taken for daily PrEP. As both regimens were well accepted, a flexible approach adopting either or both regimens with possible switching is warranted in order to suit individual health needs.

Failure of pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate and emtricitabine may occur despite perfect adherence, although this is uncommon. Failure results in breakthrough HIV infection. Delayed seroconversion associated with antiretroviral use may complicate the picture, causing uncertainties in interpreting adherence patterns for establishing the true cause of PrEP failure.

Recombination is an important feature of HIV evolution, occurring both within and between the major branches of diversity (subtypes). The Ugandan epidemic is primarily composed of two subtypes, A1 and D, that have been co-circulating for 50 years, frequently recombining in dually infected patients. Here, we investigate the frequency of recombinants in this population and the location of breakpoints along the genome. As part of the PANGEA-HIV consortium, 1,472 consensus genome sequences over 5 kb have been obtained from 1,857 samples collected by the MRC/UVRI & LSHTM Research unit in Uganda, 465 (31.6 per cent) of which were near full-length sequences (>8 kb). Using the subtyping tool SCUEAL, we find that of the near full-length dataset, 233 (50.1 per cent) genomes contained only one subtype, 30.8 per cent A1 (n = 143), 17.6 per cent D (n = 82), and 1.7 per cent C (n = 8), while 49.9 per cent (n = 232) contained more than one subtype (including A1/D (n = 164), A1/C (n = 13), C/D (n = 9); A1/C/D (n = 13), and 33 complex types). K-means clustering of the recombinant A1/D genomes revealed a section of envelope (C2gp120-TMgp41) is often inherited intact, whilst a generalized linear model was used to demonstrate significantly fewer breakpoints in the gag–pol and envelope C2-TM regions compared with accessory gene regions. Despite similar recombination patterns in many recombinants, no clearly supported circulating recombinant form (CRF) was found, there was limited evidence of the transmission of breakpoints, and the vast majority (153/164; 93 per cent) of the A1/D recombinants appear to be unique recombinant forms. Thus, recombination is pervasive with clear biases in breakpoint location, but CRFs are not a significant feature, characteristic of a complex, and diverse epidemic. 1. Introduction 2. Methods 2.1 Sample collection 2.2 Sequencing and alignment 2.3 Subtyping 2.4 Identification of transmitted breakpoints 2.5 Recombination pattern classification 2.6 Breakpoint and genome location model framework 3. Results 3.1 Subtype distribution 3.2 Identification of CRFs and transmitted breakpoints 3.3 Recombinant groupings 3.4 Breakpoint distribution 4. Discussion

Introduction Sexual acquisition has emerged as a transmission route for hepatitis C virus (HCV) of growing importance among human immunodeficiency virus (HIV)‐positive populations. In Western countries, HCV epidemics have been increasingly detected among men who have sex with men (MSM). This review describes the molecular epidemiology of sexually acquired HCV infection in the Asia‐Pacific region. Methods A systematic search was performed on PubMed in March 2019. Either abstract or full‐text of each publication in the search results was screened for eligibility. Studies from different countries/cities involving eligible cases, who acquired HCV sexually with identified subtype, were synthesized for the evaluation of molecular epidemiology in the Asia‐Pacific region. Two large‐scale systematic reviews on the genotype distribution of HCV at a population level and among PWID were used as references for comparison. Results and discussion Overall, 13 full‐text articles with 549 subjects originating from nine countries/cities were reviewed. A total of five genotypes and 14 subtypes were identified, dominated by subtypes 1b (23.0%), 2a (19.1%) and 3a (29.5%). A majority of the infected cases occurred in HIV‐positive MSM. In some places, notably Hong Kong, India and Indonesia, the predominant subtype in sexually acquired HCV infection in MSM was different from that circulating in the general population. Shared transmission networks between people who inject drugs (PWID) and MSM were shown in Australia and New Zealand, whereas overlapping risk elicited from a small number of subjects existed in Tokyo, Taipei and Guangxi. MSM‐specific clusters were identified in Hong Kong, Taipei and Hubei. Conclusions The distribution of sexually acquired HCV was sparsely scattered across countries/cities in the Asia‐Pacific region. The threat of overlapping risk differed by locations, whereas transnational outbreaks remained uncommon. The paucity of information has hindered progress with comprehensive assessment in the Asia‐Pacific region, where seroprevalence of HCV among HIV‐positive MSM was relatively high.

Introduction Pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate (TDF) 300 mg/emtricitabine (FTC) 200 mg is a proven strategy for preventing human immunodeficiency virus (HIV) transmission in men who have sex with men (MSM). This study aimed to test the feasibility and acceptability of PrEP delivered at a pilot clinic for MSM in Hong Kong, where PrEP service is currently unavailable. Methods Partially self-financed PrEP was provided to HIV-negative adult MSM with high behavioural risk of HIV transmission after excluding hepatitis B infection and renal insufficiency. Participants received daily TDF/FTC for 30 weeks at 13.3% of the drug cost. Adherence and behaviours were monitored through questionnaires while creatinine and HIV/STI (sexually transmitted infection) incidence were monitored with point-of-care and laboratory tests. Preference for continuing with PrEP was evaluated at the end of the prescription period. Results Seventy-one PrEP-naive MSM were included in the study, of whom 57 (80%) were retained at the end of 28 weeks. Satisfactory adherence and self-limiting adverse events were reported, while none of the participants contracted HIV. Risk compensation was observed, with an STI incidence of 3.17 per 100 person-years. At the end of the prescription period, a majority (89%) indicated interest in continuing with PrEP. Preference for PrEP was associated with age ≥28 years and peer influence (P=0.04), while stigma was a concern. Price was a deterrent to self-financed PrEP, and only half (51%) considered a monthly cost of ≤HK$500 (US$1=HK$7.8) as reasonable. Conclusions A partially self-financed mode of PrEP delivery is feasible with good retention in MSM in Hong Kong.

Background Previous studies have shown that men who have sex with men (MSM) and who engage in drug use in sexualized contexts (chemsex) were more likely to be HIV positive. Their social networks and adoption of HIV prevention measures have, however, not been fully investigated. We aim to compare the sexual behavior, HIV prevention efforts and social networks of MSM by the intensity and patterns of their drug use. Methods Data from respondents of a community-based, cross-sectional survey (PRiSM) conducted among MSM in Hong Kong in 2017 were collected retrospectively. Characteristics of MSM engaged and not engaged in chemsex were compared in logistic regressions, delineated by latent class analysis (LCA) and compared in multinominal logistic regression. Findings Of 4133 respondents, 3044 were sexually active with an HIV prevalence of 6.5%. The prevalence of chemsex engagement in the preceding 6 months was 12%, after excluding use of poppers or erectile dysfunction agents (EDA) alone. Four types of drug user were identified by LCA: Minimal (mainly poppers), low-threshold (mainly poppers and EDA), medium-threshold (mainly methamphetamine, GHB, poppers and EDA) and intense (extensive use of different types of drug). Medium-threshold and intense drug users were more likely to be HIV positive, be diagnosed with sexually transmitted infections, make gay friends through mobile apps and sex parties, and intend to take pre-exposure prophylaxis (PrEP). Medium-threshold drug users had a more influential role in their social network, as shown by their higher centrality in mobile apps network. Conclusion Chemsex engagement in MSM is significantly associated with HIV infection in Hong Kong. The HIV transmission risk could however be offset by the inclination of MSM belonging to medium-threshold and intense drug users to take PrEP, should the intervention become accessible to the community. Further mobile apps could be a good channel to access MSM who are medium-threshold drug users.

BackgroundHIV spread in injecting drug users (IDU) occurs efficiently between individuals within their social networks. While methadone maintenance treatment has long known to be effective in combating HIV transmission in IDU, the impacts of one's social connections and HIV status have not been well characterised. A study was conducted with the objective of differentiating the pattern of treatment participation between HIV-positive and negative methadone users and to understand its association with social connections with peers.MethodsAttendance data in one calendar year were extracted from a territory-wide electronic clinical record database of over 8000 methadone users attending 19 clinics in Hong Kong, a city with a relatively low HIV prevalence in injecting drug users. A case-control design was used by matching HIV positive methadone users with HIV negative controls. A temporal-social co-occurrence approach was adopted to construct a social network. Multiple logistic regression and network-based analyses were conducted.ResultsIn 2016, a total of 8332 methadone users had attended a clinic at least once, giving 1694016 attendance records that were included in the study. Some 432 methadone, 54 of whom HIV positive, were included in the case-control analyses. Multivariable logistic regression model showed that HIV-positive status was associated with drug injection history (adjusted odds ratio [aOR] 2.28, 95% confidence interval [95% CI] 1.19-4.38), not working fulltime (aOR 3.34, 95% CI 1.15-9.72), ethnic minority (aOR 2.59, 95% CI 1.33-5.02) and minimum daily dose of at least 20mg (aOR 3.64, 95% CI 1.08-12.26). Those having connections with other peers were older (aOR 1.02, 95% CI 1.00-1.04), had a higher mode dose (aOR 1.03, 95% CI 1.02-1.04) and had been admitted to methadone programme for longer time (aOR 1.07, 95% CI 1.02-1.13). Among those with connections, HIV-negative users did not have more connections (median degree centrality 21.00 vs 34.50, p = 0.26) but the network structure was stronger (clustering coefficient 0.65 vs 0.53, p = 0.03).ConclusionThe weak and sparse linkages may explain the generally low HIV prevalence and incidence in opioid-dependent persons in Hong Kong. Social support could play a constructive role in harm reduction and ethnic minority community-based organisations could help and reinforce treatment adherence.

Background: Pre-exposure prophylaxis (PrEP) is currently an important tool for HIV prevention, especially in communities with higher risk of infection, notably men who have sex with men (MSM). To date, PrEP has remained generally unavailable in many cities around the world. In the planning of strategies for PrEP targeting MSM, community assessment is crucial to understand members’ responses to the new intervention. Objective: Awareness and acceptance are 2 different but intricately linked contexts of PrEP. The aim of this study was to identify the determinants of awareness and acceptance of PrEP among MSM and to delineate their interrelationships in Hong Kong where PrEP services have not been developed. Methods: A Web-based questionnaire survey was administered in light of the popularity of the internet as a platform for information and networking in the MSM community. Factors associated with PrEP acceptance and awareness were separately analyzed, and their predictors were subsequently tested by multivariate logistic regression. Associations between acceptance and awareness of PrEP were examined by factor network analysis. Results: Between August and September 2016, results from a total of 453 HIV-negative MSM were analyzed. Half (49.7%, 225/453) of the respondents were aware of PrEP, and 78.3% (355/453) would consider using PrEP when it becomes available. Awareness of PrEP was associated with recent (P=.01) and ongoing (P=.04) use of psychotropic drugs for sex (chemsex). MSM who used online forums to seek sex partners had lower awareness (P=.04) than those visiting physical venues for sex networking. MSM who accepted PrEP were more likely users of internet channels for sex networking (P=.049), especially location-based social network apps (P=.04). MSM accepting PrEP were more concerned about their partners’ HIV status (P=.002), history of sexually transmitted infections (P=.01), condom use (P=.02), and HIV testing behavior (P=.02). Multivariate logistic regressions revealed that PrEP awareness was related to one’s networking pattern, whereas its acceptance was associated with inclination to self-protect from HIV. Factor network analysis highlighted the importance of chemsex, which was linked by over half of the edges, whereas the rest were contributed by HIV testing behaviors. Conclusions: In Hong Kong, the overall awareness among MSM toward PrEP was only moderate but their acceptance was higher. Targeting MSM with chemsex behaviors through Web-based platforms and parallel development of tailored HIV testing services are important when introducing PrEP in the community.

Summary Objective To assess the potential risk of dengue transmission in a non-endemic city using a spatial epidemiological approach. Methods Past dengue exposure of the general population was examined by dengue virus (DENV) IgG testing of archived samples from voluntary blood donors. Vector intensities were determined by local ovitrap index (OI). Analyses were made in the context of population statistics at both the district and sub-district level. Results The overall prevalence of DENV IgG was low at 2.25%. Positive donors were more likely to be older, non-Chinese, and female. Neither the OI nor the location of residence was associated with DENV serology. The sub-district level OI was clustered, but no correlation could be confirmed with the location of residence of positive blood donors. Conclusions The cumulative exposure of Hong Kong residents to dengue has so far been low. Coupled with the lack of a spatial relationship between exposed cases and vector intensities, a high risk of local transmission of DENV is not supported. The apparently higher exposure likelihood of females could be explained by past infection in workers from dengue endemic countries, while frequent travel could have exposed older adults to DENV. Continued surveillance, risk assessment, and intensive vector control remain essential to prevent the transformation of a non-endemic to an endemic city.

Background Adherence to monitoring and prescription of pre-exposure prophylaxis (PrEP) is important in effectively preventing HIV infection. We aimed to establish the retention rate of men who have sex with men (MSM) who enrolled in a PrEP implementation study in Hong Kong, China. Methods Our study was a survival analysis of a crossover study. A research clinic was set up in the teaching hospital of the university to recruit participants through community-based organisations or by self-referral. Participants were randomly assigned by block randomisation with a block size of four to two groups during the study period (32 weeks split into two 16-week phases); in the first group, participants were asked to take PrEP every day for the first 16 weeks then on demand for the remaining 16 weeks, and in the second group, participants took PrEP on demand for the first 16 weeks then ever day for the remaining 16 weeks. Eligible participants were adult HIV-negative MSM with a history of high HIV-risk behaviours or sexually transmitted infections in the preceding 6 months and an inclination to practice condomless sex in the coming 6 months. The exclusion criteria were hepatitis B virus infection, creatinine clearance lower than 60 mL per min, with or without mental illnesses. We assessed behavioural factors associated with retention by bivariate analysis. We used cox regression to characterise participants who had dropped out of the study. The study was approved by the Joint Chinese University of Hong Kong-New Territories East Cluster Clinical Research Ethics Committee (CREC 2016.719). The trial is registered with the Centre for Clinical Research and Biostatistics, The Chinese University of Hong Kong, Hong Kong, China (trial number CUHK_CCRB00606). Findings Between Aug 25, 2018, and Mar 23, 2019, we recruited 120 MSM. Of the 120 MSM recruited, one ( Interpretation The retention was high in a trial setting. Defaulters who had receptive anal sex or HIV-positive sex partners might have continued HIV risk, therefore other prevention measures should be made available if PrEP was not sought elsewhere. The role of intimate or sex partners in retention in PrEP programmes should be explored. Funding AIDS Trust Fund (MSS 292 R).

Summary: Background: Transmission dynamics of SARS-CoV-2 varied by the settings of virus exposure. Understanding the inter-relationship between exposure setting and transmission networks would provide a basis for informing public health control strategies. Methods: Surveillance and clinical data from the first wave of COVID-19 outbreaks in Hong Kong were accessed. Twelve exposure setting types were differentiated – household, neighbourhood, eateries, entertainment, parties, shopping, personalised service, workplace, education, worship, healthcare, transport. Clustering was investigated followed by reconstructing the transmission cascades of clustered cases using social networking approach. Linked and unlinked cases were compared in statistical analyses. Findings: Between 23 January and 19 June 2020, 1128 cases were reported. Among 324 cases related to local transmission, 123 clusters comprising two or more epidemiologically linked cases were identified. Linked cases had lower Ct value (p 1 exposure setting, with a median reproduction number of 3(IQR: 2–4), versus 1(IQR:1–2) for cascades involving a single setting (n = 36 cascades). The longest cascade featured a bar (entertainment) as primary setting, with propagation through 30 non-primary exposure settings from seven setting types, reflecting, propensity for widespread dispersion and difficulty in containment. Interpretation: There was marked heterogeneity in the characteristics of SARS-CoV-2 transmission cascades which differed by exposure setting. Network epidemiological analyses of transmission cascades can be applied as a risk assessment tool in decision-making for calibrating social distancing measures. Funding: Health and Medical Research Fund

HIV testing is the gateway to biomedical means of prevention and treatment. Identifying predictors of HIV testing is important to inform future preventive interventions. Of 444 men who have sex with men without known HIV infection enrolled in a study in Hong Kong, 64% had ever been HIV-tested. Testers were generally older, better educated, had a higher monthly income, and more likely self-identified as gay. Testers often used Internet and frequented saunas for sex networking, compared with non-testers attending bars, massage centres and public toilets. HIV testing habit also varied with the profile of body image type and preferred type in sex networking. Higher acceptance of pre-exposure prophylaxis (PrEP) was observed among testers. Overall, socioeconomic status played an important role in both HIV testing and access to PrEP. Interventions targeting sex networking venues and alternative means of testing provision are needed to increase coverage of HIV testing.

Background Understanding the driving forces of HIV infection is crucial for developing intervention strategies. We aimed to infer these forces from genetic linkages between past and newly diagnosed cases by a molecular approach. Methods We recruited newly diagnosed HIV patients from all three HIV specialist clinics in Hong Kong, China, between 2016 and 2018 to collect their HIV sequences with corresponding behavioural and clinical data. We retrieved archived HIV sequences from 1994 to 2012 separately. We pooled and analysed sequences by constructing a network with 1·5% TN93 distance threshold and measured node degree centrality. We did univariate analyses to identify factors associated with genetic links with archived sequences among newly diagnosed patients, and used a generalised linear model to differentiate archived sequences having links with new cases adjusting for diagnosis year. Findings 2778 partial pol sequences were amalgamated for network construction, of which 426 were newly diagnosed. The network contained 1908 (69%) nodes and 23 305 edges. Some 703 (3%) edges linked 192 archived samples with 135 new cases. Of 239 newly diagnosed patients with genetic connections, those linked with past infections were more likely to be subtype B (odds ratio 3·31; p Interpretation HIV transmission chains linking new with past infections in Hong Kong were driven by younger MSM. Chemsex, emergence in recent years, only clustered in and contributed to some new infections. Formation of transmission linkages over time signified the importance of targeting new and established infections in developing prevention strategies. Funding Research Grants Council of Hong Kong (14103315) and AIDS Trust Fund (MSS 229 R and 243 R).

BackgroundWhile HIV incidence among men who have sex with men (MSM) is increasing in Hong Kong, unprotected sex apparently remains prevalent among those infected but virally non-suppressed. Little is known about how sexual behaviours and sexual connections may change among MSM along their HIV care continuum.MethodsIn this retrospective cross-sectional study, HIV-positive MSM attending the largest HIV specialist clinic in Hong Kong between October and December 2014 were invited to complete a self-administrated structured questionnaire. Their behavioural profile and partner sourcing patterns during the one-year period respectively (a) before HIV diagnosis, (b) after HIV diagnosis, (c) after initiation of antiretroviral treatment and (d) preceding the survey were examined.ResultsOf 345 recruited MSM, 304 (88.1%) had treatment initiated and 272 (78.8%) had viral load suppressed. In the first year after HIV diagnosis, the proportion reporting inconsistent condom use dropped from 47.0% to 17.5% (pConclusionsMost HIV-positive MSM had persistently low level of sexual risk behaviours along their care continuum and achieved viral load suppression, conferring a general reduction of secondary transmission risk in Hong Kong. To increase the effectiveness of Treatment as Prevention strategy, uptake of HIV testing for undiagnosed HIV-positive MSM shall be emphasised.

Background In Hong Kong, pre-exposure prophylaxis (PrEP) was first launched as a pilot study for men who have sex with men (MSM) at high risk of HIV infection. However, the community's acceptance of such programme might affect policy making in its implementation as a service. Therefore, we aimed to examine the feasibility of an incentivised mode of PrEP delivery in the MSM community. Methods We did a implementation study of daily co-formulated tenofovir disoproxil fumarate 300 mg plus emtricitabine 200 mg (TDF/FTC). We prescribed oral tablets of TDF/FTC to PrEP-naive, HIV-negative, high-risk MSM for 30 weeks through a pilot clinic in Hong Kong. We assessed MSM that self-referred or were referred by collaborating community organisations or HIV services using a survey about their eligibility and, if applicable, reasons for not joining the study. The key inclusion criteria were recent history of condomless anal sex and HIV negative on testing, whereas HBsAg-positive patients and those with impaired renal functions were excluded. The primary measures were acceptance rate and associated socio-behavioural factors. Consenting MSM were required to pay a fixed price at each visit but the follow-up interval was increased over time, such that the unit cost of TDF/FTC became lower for participants who remained on the programme. The actual cost of TDF/FTC was equivalent to HK$25 (US$3·20) per tablet or 13% of the market price upon completion. The study was approved by the Joint Chinese University of Hong Kong–New Territories East Cluster Clinical Research Ethics Committee. This study is registered with the Centre for Clinical Research and Biostatistics Clinical Trials Registry, number CUHK_CCRB00533, and the Chinese Clinical Trial Registry, number ChiCTR-OPC-16009603. Findings Between Sep 21, 2017, and May 23, 2018, 292 MSM were assessed. Among 247 MSM who showed interest in the study, 196 (79%) had engaged in high-risk behaviours in the preceding 6 months. Among 229 high risk MSM, 196 (86%) indicated willingness to join the study, of which 71 ultimately enrolled. 49 (98%) of 50 MSM who used drugs during sex were interested in joining the programme (p=0·004). There were no significant associations between risky behaviours, such as the practice of condomless sex, and PrEP acceptance. The most common reason for not being interested in the study was the drug cost (24 [53%] of 45), concern about side-effects (13 [29%]), low perceived risk (ten [22%]), and feeling troublesome about taking daily medications (nine [20%]). Interpretation An incentivised mode of PrEP delivery was moderately well accepted by high risk MSM in Hong Kong. The gap between awareness and their access to PrEP would need to be addressed in the future if programme expansion is considered, since price can be a major deterrent for some eligible people despite the lowered price. Community education on PrEP together with pre-PrEP counselling is crucial for successful implementation. Funding AIDS Trust Fund (MSS 264 R), Hong Kong.

Background Improved understanding of network structure—one of the driving forces of HIV transmission—could facilitate the design of interventions. We aimed to assess the structure of HIV transmission networks and their relationship to newly diagnosed cases in Hong Kong, where sexual transmission between men prevails. Methods We used HIV gag-pol sequences collected over a 20-year period from all major HIV services in Hong Kong to construct transmission networks. We identified network clusters and decomposed them by modularity if one contained more than half of the connected nodes. We analysed network size, average degree, and epidemiological metrics, and examined sequences of newly diagnosed cases in a cross-sectional study to assess growth of identified clusters. Findings A total of 2352 archived HIV sequences collected in 1994–2013 were retrieved, alongside HIV sequences from 81 cases diagnosed between Aug 4, 2016, and Jan 17, 2017. The transmission network with a density of 1·58% contained 1801 (74%) nodes that were linked to at least one other node. Network degree followed a power law distribution (correlation 0·988). There were 72 dyads and 64 clusters with at least three nodes. The largest connected component contained more than half of the connected nodes (1282 [71%]) and thus was decomposed into 20 clusters. Of 83 clusters included in the analysis, 10 were linked to 37 (46%) new cases. The sizes of incident clusters were significantly larger (p vs 4 [IQR 3-8]) with a higher mean degree (p vs 2·80 [IQR 2·00–4·64]). Clusters with newly diagnosed patients had higher transmission speeds (p vs 0·24 [IQR 0·17–0·44] ppy). Clusters with new cases in 2016 had a higher 3-year cluster incidence in 2013 (p Interpretation Hong Kong's HIV transmission was a preferential attachment process as inferred from the power law degree distribution elicited. The HIV epidemic has grown from existing clusters with large size, degree, and transmission speed. Disassortative age mixing could have predisposed younger individuals to transmission risk from older patients. Funding Research Grants Council of Hong Kong (14103315), AIDS Trust Fund (MSS 229 R, 243 R).

Background The low-threshold methadone maintenance treatment (MMT) programme in Hong Kong has been in place for about 40 years. Assessment of the participation pattern of methadone users may inform future programme development to achieve effective harm reduction. Methods Longitudinal clinical data of methadone users who first registered for MMT in the year 2008 in Hong Kong were retrieved after ethical and institutional approval. Participation pattern of this cohort was evaluated by examining users’ frequency of attendance and then the overall retention rate. A subgroup of consistent users who remained on treatment in 2012 and/or 2013 was analysed. Comparison was made between high- and low-frequency users, and among high/moderate and low consistency users, to test their correlations with socio-demographics and social connectivity. Results The cohort of methadone users registering in the year 2008 was composed of 351 persons, 77 % of whom were ethnic Chinese, with a median age of 34 and the duration of heroin dependency of 6 years. The participation pattern of methadone users was highly variable, with a 6-year retention rate of 38 %. Discontinuations or 'breaks' of >28 days had occurred in 212 (60 %) methadone users. About one third (n = 117) were high-frequency users who had attended more than twice a week for at least 90 % of their treatment periods. The dosages received by high-frequency users were generally higher. Of those continuing on treatment in the fifth and/or sixth year (n = 185), 30 (16 %), 29 (16 %) and 126 (68 %) gave a high, moderate and low level of consistency as defined by the lengths of breaks. High/moderate consistency users had a longer history of heroin use and a higher degree of connectivity with other users by social network analysis. Conclusions Despite the variability of frequency and consistency of attendance of drug users enrolling in the low-threshold MMT programme in Hong Kong, a consistent pattern could be seen in the proportional distribution of dosage and participation efforts. Whereas an adequate dosage was a potential predictor of optimal frequency of attendance, demographics and connectivity had varied between continued users with different levels of consistency.