HIV Transmission Patterns Research Articles

Analysis of Multi-Interacting Networks and Their Application to HIV Transmission Among Men Who Have Sex with Men

Network science is a powerful tool for understanding the complex interactions between individuals and is widely used to study the spread of infectious diseases. Men who have sex with men (MSM) have a high risk of HIV transmission, and sex-role preference is an essential element of HIV spread. Considering the preferences of MSM groups and the effective connections with actual transmission rates, this study established a random network (symmetric degree distribution) and a scale-free network (asymmetric degree distribution), respectively. The matrix centrality theory and computer numerical simulation are combined to analyze HIV transmission patterns in MSM groups. The results indicate that the stochasticity in the asymmetric degree distribution network is higher than in the symmetric degree distribution network. Degree and eigenvector centrality are similar in asymmetric or symmetric degree distribution networks. The centrality eigenvector can reflect more information because it includes both the node’s degree and its connections’ degrees. However, when many individuals are infected, the degree of centrality may directly come into play.

Exploring the seasonality and optimal control strategy of HIV/AIDS epidemic in China: The impact of seasonal testing.

In this work, we investigate how the seasonal variation in the number of individuals who are tested for an HIV antibody in outpatient clinics affects the HIV transmission patterns in China, which has not been well studied. Based on the characteristics of outpatient testing data and reported cases, we establish a periodic infectious disease model to study the impact of seasonal testing on HIV transmission. The results indicate that the seasonal testing is a driving factor for the seasonality of new cases. We demonstrate the feasibility of ending the HIV/AIDS epidemic. We find that the diagnostic rates related to testing play a crucial role in controlling the size of the epidemic. Specifically, when considering minimizing both infected individuals and diagnostic rates, the level of attention paid to undiagnosed infected individuals is always positively correlated with the optimal diagnostic rates, while the optimal diagnostic rates are negatively correlated with the size of the epidemic at the terminal time.

Epidemiological characteristics of HIV transmission in southeastern China from 2015 to 2020 based on HIV molecular network.

HIV/AIDS remains a global public health problem, and understanding the structure of social networks of people living with HIV/AIDS is of great importance to unravel HIV transmission, propose precision control and reduce new infections. This study aimed to investigate the epidemiological characteristics of HIV transmission in Fujian province, southeastern China from 2015 to 2020 based on HIV molecular network. Newly diagnosed, treatment-naive HIV/AIDS patients were randomly sampled from Fujian province in 2015 and 2020. Plasma was sampled for in-house genotyping resistance test, and HIV molecular network was created using the HIV-TRACE tool. Factors affecting the inclusion of variables in the HIV molecular network were identified using univariate and multivariate logistic regression analyses. A total of 1,714 eligible cases were finally recruited, including 806 cases in 2015 and 908 cases in 2020. The dominant HIV subtypes were CRF01_AE (41.7%) and CRF07_BC (38.3%) in 2015 and CRF07_BC (53. 3%) and CRF01_AE (29.1%) in 2020, and the prevalence of HIV drug resistance was 4.2% in 2015 and 5.3% in 2020. Sequences of CRF07_BC formed the largest HIV-1 transmission cluster at a genetic distance threshold of both 1.5 and 0.5%. Univariate and multivariate logistic regression analyses showed that ages of under 20 years and over 60 years, CRF07_BC subtype, Han ethnicity, sampling in 2015, absence of HIV drug resistance, married with spouse, sampling from three cities of Jinjiang, Nanping and Quanzhou resulted in higher proportions of sequences included in the HIV transmission molecular network at a genetic distance threshold of 1.5% (p < 0.05). Our findings unravel the HIV molecular transmission network of newly diagnosed HIV/AIDS patients in Fujian province, southeastern China, which facilitates the understanding of HIV transmission patterns in the province.

Psycho-Social Impact of Stigmatization against Pregnant Women with HIV

Background: Stigmatization, discrimination, and poor social support are challenges faced by people living with HIV, and the stigmatization of pregnant women with HIV is still very frequent, which can have a profound negative impact on patient's health. This can have a psychosocial impact on the sufferer. Objective: To study and determine the psychosocial impact of discriminatory behavior towards pregnant patients with HIV. Methods: This is a case report of two cases of pregnant women with HIV at the Voluntary Counseling and Testing (VCT) Polyclinic of RSUP Prof. Dr. I.G.N.G. Go to Denpasar. In-depth interviews were conducted with them regarding their views on openness to their families and communities about their condition. Results and Discussion: It was reported that two cases of pregnant women with HIV who were carrying out antenatal care in the Obstetrics and Gynecology Polyclinic Room, Prof. dr. I.G.N.G Ngoerah Central General Hospital Denpasar. In both cases, discriminatory treatment and stigma still strongly haunt the sufferers even though the form and source are slightly different. In the first case, the patient was afraid of getting discriminatory treatment and stigmatization that came from the family environment and the wider environment. Meanwhile, in the second case, it shows that the discriminatory treatment that causes stigma does not only come from far away but also comes from the people themselves. Both have a psychosocial impact that creates a sense of social discomfort, even though the race is slowly diminishing with the assistance of a counselor. There is a need for a wide range of active education by health workers to the patient's family and the community in reducing the stigma and discrimination against pregnant women with HIV. Conclusion: Women with HIV, especially those who are pregnant, are still full of negative judgments, and discriminatory behavior towards them. This can cause psychosocial impacts on patients. The disparity between knowledge about unknown patterns of HIV transmission on the one hand and risky sexual behavior, on the other hand, can be one of the risk factors for contracting HIV. This also contributes to stigma and discrimination against pregnant women with HIV.

Lessons learned from community engagement regarding phylodynamic research with molecular HIV surveillance data.

The widespread implementation of molecular HIV surveillance (MHS) has resulted in an increased discussion about the ethical, human rights and public health implications of MHS. We narrate our process of pausing our research that uses data collected through MHS in response to these growing concerns and summarize the key lessons we learned through conversations with community members. The original study aimed to describe HIV transmission patterns by age and race/ethnicity among men who have sex with men in King County, Washington, by applying probabilistic phylodynamic modelling methods to HIV-1 pol gene sequences collected through MHS. In September 2020, we paused the publication of this research to conduct community engagement: we held two public-facing online presentations, met with a national community coalition that included representatives of networks of people living with HIV, and invited two members of this coalition to provide feedback on our manuscript. During each of these meetings, we shared a brief presentation of our methods and findings and explicitly solicited feedback on the perceived public health benefit and potential harm of our analyses and results. Some community concerns about MHS in public health practice also apply to research using MHS data, namely those related to informed consent, inference of transmission directionality and criminalization. Other critiques were specific to our research study and included feedback about the use of phylogenetic analyses to study assortativity by race/ethnicity and the importance of considering the broader context of stigma and structural racism. We ultimately decided the potential harms of publishing our study-perpetuating racialized stigma about men who have sex with men and eroding the trust between phylogenetics researchers and communities of people living with HIV-outweighed the potential benefits. HIV phylogenetics research using data collected through MHS data is a powerful scientific technology with the potential to benefit and harm communities of people living with HIV. Addressing criminalization and including people living with HIV in decision-making processes have the potential to meaningfully address community concerns and strengthen the ethical justification for using MHS data in both research and public health practice. We close with specific opportunities for action and advocacy by researchers.

Public Health Response to Clusters of Rapid HIV Transmission Among Hispanic or Latino Gay, Bisexual, and Other Men Who Have Sex with Men - Metropolitan Atlanta, Georgia, 2021-2022.

During February 2021-June 2022, the Georgia Department of Public Health (GDPH) detected five clusters of rapid HIV transmission concentrated among Hispanic or Latino (Hispanic) gay, bisexual, and other men who have sex with men (MSM) in metropolitan Atlanta. The clusters were detected through routine analysis of HIV-1 nucleotide sequence data obtained through public health surveillance (1,2). Beginning in spring 2021, GDPH partnered with health districts with jurisdiction in four metropolitan Atlanta counties (Cobb, DeKalb, Fulton, and Gwinnett) and CDC to investigate factors contributing to HIV spread, epidemiologic characteristics, and transmission patterns. Activities included review of surveillance and partner services interview data,† medical chart reviews, and qualitative interviews with service providers and Hispanic MSM community members. By June 2022, these clusters included 75 persons, including 56% who identified as Hispanic, 96% who reported male sex at birth, 81% who reported male-to-male sexual contact, and 84% of whom resided in the four metropolitan Atlanta counties. Qualitative interviews identified barriers to accessing HIV prevention and care services, including language barriers, immigration- and deportation-related concerns, and cultural norms regarding sexuality-related stigma. GDPH and the health districts expanded coordination, initiated culturally concordant HIV prevention marketing and educational activities, developed partnerships with organizations serving Hispanic communities to enhance outreach and services, and obtained funding for a bilingual patient navigation program with academic partners to provide staff members to help persons overcome barriers and understand the health care system. HIV molecular cluster detection can identify rapid HIV transmission among sexual networks involving ethnic and sexual minority groups, draw attention to the needs of affected populations, and advance health equity through tailored responses that address those needs.

Transmission network and phylogenetic analysis reveal older male-centered transmission of CRF01_AE and CRF07_BC in Guangxi, China

ABSTRACT In China, the number of newly reported HIV infections in older people is increasing rapidly. However, clear information on the impact of older people on HIV transmission is limited. This study aims to reveal the local HIV transmission patterns, especially how older people affect virus transmission. Subtype analysis based on available pol sequences obtained from HIV patients revealed that CRF01_AE and CRF08_BC were predominant in patients aged <50 years, whereas CRF01_AE was predominant in older people aged ≥50 years (χ 2 = 29.299, P < 0.001). A total of 25 patients (5.2%, 25/484) were identified with recent HIV infection (RHI). Transmission network analysis found 267 genetically linked individuals forming 55 clusters (2–63 individuals), including 5 large transmission clusters and 12 transmission clusters containing RHI. Bayesian phylogenetic analysis suggested that transmission events in CRF01_AE and CRF07_BC were centred on older males, while transmission events in CRF08_BC were centred on younger males. Multivariable logistic regression analysis showed that older people were more likely to cluster within networks (AOR = 2.303, 95% CI: 1.012–5.241) and that RHI was a significant factor associated with high linkage (AOR = 3.468, 95% CI: 1.315–9.146). This study provides molecular evidence that older males play a central role in the local transmission of CRF01_AE and CRF07_BC in Guangxi. Given the current widespread of CRF01_AE and CRF07_BC in Guangxi, there is a need to recommend HIV screening as part of free national medical examinations for older people to improve early detection, timely treatment, and further reduce second-generation transmission.

Impact of molecular sequence data completeness on HIV cluster detection and a network science approach to enhance detection

Detection of viral transmission clusters using molecular epidemiology is critical to the response pillar of the Ending the HIV Epidemic initiative. Here, we studied whether inference with an incomplete dataset would influence the accuracy of the reconstructed molecular transmission network. We analyzed viral sequence data available from ~ 13,000 individuals with diagnosed HIV (2012–2019) from Houston Health Department surveillance data with 53% completeness (n = 6852 individuals with sequences). We extracted random subsamples and compared the resulting reconstructed networks versus the full-size network. Increasing simulated completeness was associated with an increase in the number of detected clusters. We also subsampled based on the network node influence in the transmission of the virus where we measured Expected Force (ExF) for each node in the network. We simulated the removal of nodes with the highest and then lowest ExF from the full dataset and discovered that 4.7% and 60% of priority clusters were detected respectively. These results highlight the non-uniform impact of capturing high influence nodes in identifying transmission clusters. Although increasing sequence reporting completeness is the way to fully detect HIV transmission patterns, reaching high completeness has remained challenging in the real world. Hence, we suggest taking a network science approach to enhance performance of molecular cluster detection, augmented by node influence information.

An Alarming Shift of HIV Infection from Injection Drug to Sexual Transmission in Mashhad, Iran, 1989-2014

Introduction: Iran is facing to a rapid change in the epidemiological pattern of HIV. The trend of annual number of new HIV infections and factors associated with the development of HIV over the last two decades in Iran, were examined.&#x0D; Methods: The data were retrospectively collected from patients who attended the Behavior Diseases Consultation Center of Mashhad University of Medical Sciences in Iran. Individuals were contributed if they were HIV-positive. Baseline factors including demographic, behavioral and clinical characteristics for all participants were examined. Changes in population characteristics were assessed using chi-square test or the Fisher’s exact test.&#x0D; Results: From 1989 to 2014, 584 individuals were eligible for present analysis according to the inclusion criteria. Most patients were men (87%) with most being 36–52 years old, unemployed (58%), married (39.3%), less educated (47.7%) and had a history of imprisonment (83%). The most common modes of HIV transmission were injection drug use (IDU) (51.4%) and IDU along with the sexual relationship (26.5%). These transmission modes varied significantly according to gender (p-value&lt;0.001). Similarly, IDU and sexual relationship were most important transmission modes in males and females, respectively. The number of new HIV infections through sexual-related modes has risen sharply in recent years.&#x0D; Conclusion: In Iran, the pattern of HIV transmission is shifting from unsafe injection drug to unsafe sexual contact for forthcoming years. Also, increasing trend of HIV incidence in women is remarkable. Accordingly, HIV-prevention strategies need to be changed.

A Real-Life Action toward the End of HIV Pandemic: Surveillance of Mother-to-Child HIV Transmission in a Center from Southeast Romania.

Preventing mother-to-child HIV transmission is a strategy to eliminate new infections to move toward a world free of HIV/AIDS. The aim of this study is to assess the effectiveness of the perinatal infection prevention program in a single center from southeast Romania. Newborns of HIV-positive mothers from 2005 to 2020 were followed-up until the age of two in a retrospective study. The transmission rate from HIV-positive mothers to living children was zero, but neonatal mortality, preterm birth and birth defects were still high. The peculiarity of our study is the high proportion of mothers with a nosocomial pattern of HIV transmission. Intensifying the efforts for accurate implementing the interventions for the prevention of mother-to-child HIV transmission, a long time follow-up for HIV-exposed uninfected children and new research on related HIV pregnancies are necessary to reach the objective of a new generation free of HIV.

Evaluating whole HIV-1 genome sequence for estimation of incidence and migration in a rural South African community.

Background: South Africa has the largest number of people living with HIV (PLWHIV) in the world, with HIV prevalence and transmission patterns varying greatly between provinces. Transmission between regions is still poorly understood, but phylodynamics of HIV-1 evolution can reveal how many infections are attributable to contacts outside a given community. We analysed whole genome HIV-1 genetic sequences to estimate incidence and the proportion of transmissions between communities in Hlabisa, a rural South African community. Methods: We separately analysed HIV-1 for gag, pol, and env genes sampled from 2,503 PLWHIV. We estimated time-scaled phylogenies by maximum likelihood under a molecular clock model. Phylodynamic models were fitted to time-scaled trees to estimate transmission rates, effective number of infections, incidence through time, and the proportion of infections imported to Hlabisa. We also partitioned time-scaled phylogenies with significantly different distributions of coalescent times. Results: Phylodynamic analyses showed similar trends in epidemic growth rates between 1980 and 1990. Model-based estimates of incidence and effective number of infections were consistent across genes. Parameter estimates with gag were generally smaller than those estimated with pol and env. When estimating the proportions of new infections in Hlabisa from immigration or transmission from external sources, our posterior median estimates were 85% (95% credible interval (CI) = 78%-92%) for gag, 62% (CI = 40%-78%) for pol, and 77% (CI = 58%-90%) for env in 2015. Analysis of phylogenetic partitions by gene showed that most close global reference sequences clustered within a single partition. This suggests local evolving epidemics or potential unmeasured heterogeneity in the population. Conclusions: We estimated consistent epidemic dynamic trends for gag, pol and env genes using phylodynamic models. There was a high probability that new infections were not attributable to endogenous transmission within Hlabisa, suggesting high inter-connectedness between communities in rural South Africa.

Deep-sequence phylogenetics to quantify patterns of HIV transmission in the context of a universal testing and treatment trial - BCPP/Ya Tsie trial.

Mathematical models predict that community-wide access to HIV testing-and-treatment can rapidly and substantially reduce new HIV infections. Yet several large universal test-and-treat HIV prevention trials in high-prevalence epidemics demonstrated variable reduction in population-level incidence. To elucidate patterns of HIV spread in universal test-and-treat trials, we quantified the contribution of geographic-location, gender, age, and randomized-HIV-intervention to HIV transmissions in the 30-community Ya Tsie trial in Botswana. We sequenced HIV viral whole genomes from 5114 trial participants among the 30 trial communities. Deep-sequence phylogenetic analysis revealed that most inferred HIV transmissions within the trial occurred within the same or between neighboring communities, and between similarly aged partners. Transmissions into intervention communities from control communities were more common than the reverse post-baseline (30% [12.2 - 56.7] vs. 3% [0.1 - 27.3]) than at baseline (7% [1.5 - 25.3] vs. 5% [0.9 - 22.9]) compatible with a benefit from treatment-as-prevention. Our findings suggest that population mobility patterns are fundamental to HIV transmission dynamics and to the impact of HIV control strategies. This study was supported by the National Institute of General Medical Sciences (U54GM088558), the Fogarty International Center (FIC) of the U.S. National Institutes of Health (D43 TW009610), and the President's Emergency Plan for AIDS Relief through the Centers for Disease Control and Prevention (CDC) (Cooperative agreements U01 GH000447 and U2G GH001911).

HIV transmission patterns among transgender women, their cisgender male partners, and cisgender MSM in Lima, Peru: A molecular epidemiologic and phylodynamic analysis

SummaryBackgroundTransgender women (TW) in Peru are disproportionately affected by HIV. The role that cisgender men who have sex with TW (MSTW) and their sexual networks play in TW’s risk of acquiring HIV is not well understood. We used HIV sequences from TW, MSTW, and cisgender men who have sex with men (MSM) to examine transmission dynamics between these groups.MethodsWe used HIV-1 pol sequences and epidemiologic data collected through three Lima-based studies from 2013 to 2018 (n = 139 TW, n = 25 MSTW, n = 303 MSM). We identified molecular clusters based on pairwise genetic distance and used structured coalescent phylodynamic modeling to estimate transmission patterns between groups.FindingsAmong 200 participants (43%) found in 62 clusters, the probability of clustering did not differ by group. Both MSM and TW were more likely to cluster with members of their own group than would be expected based on random mixing. Phylodynamic modeling estimated that there was frequent transmission from MSTW to TW (67·9% of transmission from MSTW; 95%CI = 52·8–83·2%) and from TW to MSTW (76·5% of transmissions from TW; 95%CI = 65·5–90·3%). HIV transmission between MSM and TW was estimated to comprise a small proportion of overall transmissions (4·9% of transmissions from MSM, and 11·8% of transmissions from TW), as were transmissions between MSM and MSTW (7·2% of transmissions from MSM, and 32·0% of transmissions from MSTW).InterpretationThese results provide quantitative evidence that MSTW play an important role in TW’s HIV vulnerability and that MSTW have an HIV transmission network that is largely distinct from MSM.

The Role of Phylogenetics in Unravelling Patterns of HIV Transmission towards Epidemic Control: The Quebec Experience (2002-2020).

Phylogenetics has been advanced as a structural framework to infer evolving trends in the regional spread of HIV-1 and guide public health interventions. In Quebec, molecular network analyses tracked HIV transmission dynamics from 2002–2020 using MEGA10-Neighbour-joining, HIV-TRACE, and MicrobeTrace methodologies. Phylogenetics revealed three patterns of viral spread among Men having Sex with Men (MSM, n = 5024) and heterosexuals (HET, n = 1345) harbouring subtype B epidemics as well as B and non-B subtype epidemics (n = 1848) introduced through migration. Notably, half of new subtype B infections amongst MSM and HET segregating as solitary transmissions or small cluster networks (2–5 members) declined by 70% from 2006–2020, concomitant to advances in treatment-as-prevention. Nonetheless, subtype B epidemic control amongst MSM was thwarted by the ongoing genesis and expansion of super-spreader large cluster variants leading to micro-epidemics, averaging 49 members/cluster at the end of 2020. The growth of large clusters was related to forward transmission cascades of untreated early-stage infections, younger at-risk populations, more transmissible/replicative-competent strains, and changing demographics. Subtype B and non-B subtype infections introduced through recent migration now surpass the domestic epidemic amongst MSM. Phylodynamics can assist in predicting and responding to active, recurrent, and newly emergent large cluster networks, as well as the cryptic spread of HIV introduced through migration.

Integrated molecular and affiliation network analysis: Core-periphery social clustering is associated with HIV transmission patterns

This study investigates the two-mode core-periphery structures of venue affiliation networks of younger Black men who have sex with men (YBMSM). The study examined the association between these structures and HIV phylogenetic clusters, defined as members who share highly similar HIV strains that are regarded as a proxy for sexual affiliation networks. Using data from 114 YBMSM who are living with HIV in two large U.S. cities, our findings indicate that HIV phylogenetic clustering patterns were found to be associated with social clustering patterns whose members share affiliation with core venues that overlap with those of YBMSM. Distinct HIV transmission patterns were found in each city, a finding that can help to inform tailored venue-based and network intervention strategies.

Interplay Between Geography and HIV Transmission Clusters in Los Angeles County.

BackgroundClusters of HIV diagnoses in time and space and clusters of genetically linked cases can both serve as alerts for directing prevention and treatment activities. We assessed the interplay between geography and transmission across the Los Angeles County (LAC) HIV genetic transmission network.MethodsDeidentified surveillance data reported for 8186 people with HIV residing in LAC from 2010 through 2016 were used to construct a transmission network using HIV-TRACE. We explored geographic assortativity, the tendency for people to link within the same geographic region; concordant time–space pairs, the proportion of genetically linked pairs from the same geographic region and diagnosis year; and Jaccard coefficient, the overlap between geographical and genetic clusters.ResultsGeography was assortative in the genetic transmission network but less so than either race/ethnicity or transmission risk. Only 18% of individuals were diagnosed in the same year and location as a genetically linked partner. Jaccard analysis revealed that cis-men and younger age at diagnosis had more overlap between genetic clusters and geography; the inverse association was observed for trans-women and Blacks/African Americans.ConclusionsWithin an urban setting with endemic HIV, genetic clustering may serve as a better indicator than time–space clustering to understand HIV transmission patterns and guide public health action.

A Geographic Hotspot and Emerging Transmission Cluster of the HIV-1 Epidemic Among Older Adults in a Rural Area of Eastern China.

Despite the implementation of health education and free condom distribution for decades, the HIV/AIDS epidemic among older adults in China shows no sign of declining. This study aims to identify HIV transmission patterns and pathways in a rural county area and provide insight for developing effective HIV prevention strategies among older adults. Epidemiological field surveys combined with phylogenetic analysis were used to identify potential HIV transmission linkage in one rural county with a rapidly increasing HIV epidemic among older adults. A total of 160 HIV-positive individuals and their HIV-positive sexual partners diagnosed between 2015 and 2018 were recruited. Among them, 69.4% (n = 111) were diagnosed at age 50 or older, 68.1% (n = 109) were men, and 55.0% (n = 88) were married. Ninety-six participants self-reported as having been infected with HIV through commercial heterosexual behavior and 24 were infected from their HIV-positive spouse. CRF08_BC (67.0%, n = 73) and CRF07_AE (19.3%, n = 21) were the prevalent HIV stains and formed 15 clusters at distance cutoff of 0.0025. Participants diagnosed with HIV at age ≥50, those who were divorced or bereft their spouse, or infected with HIV locally were more prevalent within the 15 molecular clusters. We identified specific venues as the primary hotspot and found that commercial heterosexual contact between older men and commercial sex workers contributed to the local HIV epidemic. In rural areas with an increasing HIV epidemic, detecting HIV transmission clusters through epidemiological and phylogenetic analysis as well as designing localized HIV prevention strategies should be prioritized.

Geographic Distribution of HIV Transmission Networks in the United States

Understanding geographic patterns of HIV transmission is critical to designing effective interventions. We characterized geographic proximity by transmission risk and urban-rural characteristics among people with closely related HIV strains suggestive of potential transmission relationships. We analyzed US National HIV Surveillance System data of people diagnosed between 2010 and 2016 with a reported HIV-1 partial polymerase nucleotide sequence. We used HIV TRAnsmission Cluster Engine (HIV-TRACE) to identify sequences linked at a genetic distance of ≤0.5%. For each linked person, we assessed median distances between counties of residence at diagnosis by transmission category and urban-rural classification, weighting observations to account for persons with multiple linked sequences. There were 24,743 persons with viral sequence linkages to at least one other person included in this analysis. Overall, half (50.9%) of persons with linked viral sequences resided in different counties, and the median distance from persons with linked viruses was 11 km/7 miles [interquartile range (IQR), 0-145 km/90 miles]. Median distances were highest for men who have sex with men (MSM: 14 km/9 miles; IQR, 0-179 km/111 miles) and MSM who inject drugs, and median distances increased with increasing rurality (large central metro: 0 km/miles; IQR, 0-83 km/52 miles; nonmetro: 103 km/64 miles; IQR, 40 km/25 miles-316 km/196 miles). Transmission networks in the United States involving MSM, MSM who inject drugs, or persons living in small metro and nonmetro counties may be more geographically dispersed, highlighting the importance of coordinated health department efforts for comprehensive follow-up and linkage to care.

Brief Report: Temporal Changes in HIV Transmission Patterns Among Young Men Who Have Sex With Men, United States, 2009-2016.

In the United States, young men (aged 13-24 years) who have sex with men (MSM) bear a disproportionate burden of HIV. Transmission among MSM has been found to be disassortative by age. We analyzed HIV-1 pol sequences reported to the US National HIV Surveillance System from MSM with HIV diagnosed during 2009-2016. Using an HIV genetic transmission network, we identified persons with closely related viruses (ie, genetic distance ≤1.5%) and used multivariable logistic regression to examine changes from 2009-2012 to 2013-2016 in proportions of MSM linked to young MSM who were >5 years older or of the same race/ethnicity. Among 9510 young MSM linked to another MSM with a closely related virus, 37% linked to an older MSM and 62% linked to an MSM of the same race/ethnicity. Comparing 2013-2016 with 2009-2012, we found increases in linkage of older MSM to young MSM, with the most substantial increases seen in Hispanic/Latinos aged 13-19 [adjusted prevalence ratio (APR) = 1.31, 95% confidence interval (CI) = 1.11 to 1.56] and blacks aged 13-19 (APR = 1.23, CI = 1.06 to 1.41) and 20-24 years (APR = 1.14, CI = 1.02 to 1.28). By contrast, change in linkage patterns among racial/ethnic groups was unremarkable. We found evidence of increased age mixing among MSM with respect to HIV transmission over time, which coincides temporally with changes in partner-seeking behavior such as increased use of mobile applications. These findings indicate the importance of social factors on HIV sexual and transmission networks and suggest that prevention efforts need to effectively reach MSM of all ages.

Understanding disclosed and cryptic HIV transmission risk via genetic analysis: what are we missing and when does it matter?

To discuss the recent HIV phylogenetic analyses examining HIV transmission patterns among and within risk groups. Phylodynamic analysis has recently been applied to multiple HIV outbreaks among people who inject drugs to determine whether HIV transmission is ongoing. Large-scale analyses of datasets of HIV sequences collected for drug-resistance testing provide population-level insights into transmission patterns. One focus across world regions has been to investigate whether age-disparity is a driver of HIV transmission. In sub-Saharan Africa, researchers have examined transmission between heterosexuals and MSM and between high prevalence fishing communities and inland communities. In the US and the UK, cryptic risk groups such as nondisclosed MSM and the partners of transgender women are increasingly being uncovered based on their position in densely sampled molecular transmission networks. Analysis of HIV genetic sequence can resolve viral transmission patterns between risk groups at unprecedented scales and levels of detail. Future research should focus on understanding the effect of missing data on inferences and the biases of different methods. Uncovering groups and patterns obscured from traditional epidemiolocal analyses is exciting but should not compromise the privacy of the groups in question.