Using HIV Sequence and Epidemiologic Data to Assess the Effect of Self-referral Testing for Acute HIV Infection on Incident Diagnoses in San Diego, California

A click chemistry amplified nanopore assay for ultrasensitive quantification of HIV-1 p24 antigen in clinical samples

Despite major advances in HIV testing, ultrasensitive detection of early infection remains challenging, especially for the viral capsid protein p24, which is an early virological biomarker of HIV-1 infection. Here, To improve p24 detection in patients missed by immunological tests that dominate the diagnostics market, we show a click chemistry amplified nanopore (CAN) assay for ultrasensitive quantitative detection. This strategy achieves a 20.8 fM (0.5 pg/ml) limit of detection for HIV-1 p24 antigen in human serum, demonstrating 20~100-fold higher analytical sensitivity than nanocluster-based immunoassays and clinically used enzyme-linked immunosorbent assay, respectively. Clinical validation of the CAN assay in a pilot cohort shows p24 quantification at ultra-low concentration range and correlation with CD4 count and viral load. We believe that this strategy can improve the utility of p24 antigen in detecting early infection and monitoring HIV progression and treatment efficacy, and also can be readily modified to detect other infectious diseases.

A simple algorithm for selecting cases to investigate acute and early HIV infections in low- and middle-income countries

We documented the outcome of an over 10-year (2011-2021) effort to diagnose acute and early HIV infections (AEHI) in an Infectious Diseases Outpatient Clinic with limited resources. Of a total of 132, 119 HIV-RNA tests were performed from 2017 to 2020, 12 cases were identified, using a simple algorithm: risk exposure of 6 weeks or less before the visit and/or symptoms compatible with acute retroviral syndrome 7-30 days after exposure and/or undetermined 3rd generation rapid diagnostic test or serology. AEHI diagnoses varied from 2.4% among asymptomatic to 25% for undetermined serology cases using this simple screening applicable to different settings.

Longitudinal typing of molecular HIV clusters in a statewide epidemic

BACKGROUND

HIV molecular epidemiology is increasingly integrated into public health prevention. We conducted cluster typing to enhance characterization of a densely sampled statewide epidemic towards informing public health.

METHODS

We identified HIV clusters, categorized them into types, and evaluated their dynamics between 2004 and 2019 in Rhode Island. We grouped sequences by diagnosis year, assessed cluster changes between paired phylogenies, t0 and t1, representing adjacent years and categorized clusters as stable (cluster in t0 phylogeny = cluster in t1 phylogeny) or unstable (cluster in t0 ≠ cluster in t1). Unstable clusters were further categorized as emerging (t1 phylogeny only) or growing (larger in t1 phylogeny). We determined proportions of each cluster type, of individuals in each cluster type, and of newly diagnosed individuals in each cluster type, and assessed trends over time.

RESULTS

A total of 1727 individuals with available HIV-1 subtype B pol sequences were diagnosed in Rhode Island by 2019. Over time, stable clusters and individuals in them dominated the epidemic, increasing over time, with reciprocally decreasing unstable clusters and individuals in them. Conversely, proportions of newly diagnosed individuals in unstable clusters significantly increased. Within unstable clusters, proportions of emerging clusters and of individuals in them declined; whereas proportions of newly diagnosed individuals in growing clusters significantly increased over time.

CONCLUSION

Distinct molecular cluster types were identified in the Rhode Island epidemic. Cluster dynamics demonstrated increasing stable and decreasing unstable clusters driven by growing, rather than emerging clusters, suggesting consistent in-state transmission networks. Cluster typing could inform public health beyond conventional approaches and direct interventions.

Phylogenetic Networks and Parameters Inferred from HIV Nucleotide Sequences of High-Risk and General Population Groups in Uganda: Implications for Epidemic Control

Phylogenetic inference is useful in characterising HIV transmission networks and assessing where prevention is likely to have the greatest impact. However, estimating parameters that influence the network structure is still scarce, but important in evaluating determinants of HIV spread. We analyzed 2017 HIV pol sequences (728 Lake Victoria fisherfolk communities (FFCs), 592 female sex workers (FSWs) and 697 general population (GP)) to identify transmission networks on Maximum Likelihood (ML) phylogenetic trees and refined them using time-resolved phylogenies. Network generative models were fitted to the observed degree distributions and network parameters, and corrected Akaike Information Criteria and Bayesian Information Criteria values were estimated. 347 (17.2%) HIV sequences were linked on ML trees (maximum genetic distance ≤4.5%, ≥95% bootstrap support) and, of these, 303 (86.7%) that consisted of pure A1 (n = 168) and D (n = 135) subtypes were analyzed in BEAST v1.8.4. The majority of networks (at least 40%) were found at a time depth of ≤5 years. The waring and yule models fitted best networks of FFCs and FSWs respectively while the negative binomial model fitted best networks in the GP. The network structure in the HIV-hyperendemic FFCs is likely to be scale-free and shaped by preferential attachment, in contrast to the GP. The findings support the targeting of interventions for FFCs in a timely manner for effective epidemic control. Interventions ought to be tailored according to the dynamics of the HIV epidemic in the target population and understanding the network structure is critical in ensuring the success of HIV prevention programs.

Implementing Rapid Initiation of Antiretroviral Therapy for Acute HIV Infection Within a Routine Testing and Linkage to Care Program in Chicago

Growing evidence suggests that rapid initiation of antiretroviral therapy for HIV improves care continuum outcomes. We evaluated process and clinical outcomes for rapid initiation in acute HIV infection within a multisite health care–based HIV testing and linkage to care program in Chicago. Through retrospective analysis of HIV testing data (2016-2017), we assessed linkage to care, initiation of antiretroviral therapy, and viral suppression. Of 334 new HIV diagnoses, 33 (9.9%) individuals had acute HIV infection. Median time to linkage was 11 (interquartile range [IQR]: 5-19.5) days, with 15 days (IQR 5-27) to initiation of antiretroviral therapy. Clients achieved viral suppression at a median of 131 (IQR: 54-188) days. Of all, 69.7% were retained in care, all of whom were virally suppressed. Sites required few additional resources to incorporate rapid initiation into existing processes. Integration of rapid initiation of antiretroviral therapy into existing HIV screening programs is a promising strategy for scaling up this important intervention.

Dynamics and Dispersal of Local HIV Epidemics Within San Diego and Across The San Diego-Tijuana Border

BACKGROUND

Evolutionary analyses of well-annotated HIV sequence data can provide insights into viral transmission patterns and associated factors. Here, we explored the transmission dynamics of the HIV-1 subtype B epidemic across the San Diego (US) - Tijuana (Mexico) border region to identify factors that could help guide public health policy.

METHODS

HIV pol sequences were collected from people with HIV in San Diego County and from Tijuana between 1996-2018. A multistep phylogenetic approach was used to characterize the dynamics of spread. The contribution of geospatial factors and HIV risk group to the local dynamics were evaluated.

RESULTS

Phylogeographic analyses of the 2,034 sequences revealed an important contribution of local transmission in sustaining the epidemic, as well as a complex viral migration network across the region. Geospatial viral dispersal between San Diego communities occurred predominantly among men-who-have-sex with-men with central San Diego being the main source (34.9%) and recipient (39.5%) of migration events. HIV migration was more frequent from San Diego county towards Tijuana than vice versa. Migrations were best explained by driving time between locations.

CONCLUSION

The US-Mexico border may not be a major barrier to the spread of HIV, which may stimulate coordinated transnational intervention approaches. Whereas a focus on central San Diego has the potential to avert most spread, the substantial viral migration independent of central San Diego shows that county-wide efforts will be more effective. Combined, this work shows that epidemiological information gleaned from pathogen genomes can uncover mechanisms that underlie sustained spread and, in turn, can be a building block of public health decision making.

Molecular network-based intervention brings us closer to ending the HIV pandemic

Precise identification of HIV transmission among populations is a key step in public health responses. However, the HIV transmission network is usually difficult to determine. HIV molecular networks can be determined by phylogenetic approach, genetic distance-based approach, and a combination of both approaches. These approaches are increasingly used to identify transmission networks among populations, reconstruct the history of HIV spread, monitor the dynamics of HIV transmission, guide targeted intervention on key subpopulations, and assess the effects of interventions. Simulation and retrospective studies have demonstrated that these molecular network-based interventions are more cost-effective than random or traditional interventions. However, we still need to address several challenges to improve the practice of molecular network-guided targeting interventions to finally end the HIV epidemic. The data remain limited or difficult to obtain, and more automatic real-time tools are required. In addition, molecular and social networks must be combined, and technical parameters and ethnic issues warrant further studies.

Pretreatment HIV drug resistance spread within transmission clusters in Mexico City

BACKGROUND

Pretreatment HIV drug resistance (HIVDR) to NNRTIs has consistently increased in Mexico City during the last decade.

OBJECTIVES

To infer the HIV genetic transmission network in Mexico City to describe the dynamics of the local HIV epidemic and spread of HIVDR.

PATIENTS AND METHODS

HIV pol sequences were obtained by next-generation sequencing from 2447 individuals before initiation of ART at the largest HIV clinic in Mexico City (April 2016 to June 2018). Pretreatment HIVDR was estimated using the Stanford algorithm at a Sanger-like threshold (≥20%). Genetic networks were inferred with HIV-TRACE, establishing putative transmission links with genetic distances <1.5%. We examined demographic associations among linked individuals with shared drug resistance mutations (DRMs) using a ≥ 2% threshold to include low-frequency variants.

RESULTS

Pretreatment HIVDR reached 14.8% (95% CI 13.4%-16.2%) in the cohort overall and 9.6% (8.5%-10.8%) to NNRTIs. Putative links with at least one other sequence were found for 963/2447 (39%) sequences, forming 326 clusters (2-20 individuals). The inferred network was assortative by age and municipality (P < 0.001). Clustering individuals were younger [adjusted OR (aOR) per year = 0.96, 95% CI 0.95-0.97, P < 0.001] and less likely to include women (aOR = 0.46, 95% CI 0.28-0.75, P = 0.002). Among clustering individuals, 175/963 (18%) shared DRMs (involving 66 clusters), of which 66/175 (38%) shared K103N/S (24 clusters). Eight municipalities (out of 75) harboured 65% of persons sharing DRMs. Among all persons sharing DRMs, those sharing K103N were younger (aOR = 0.93, 95% CI 0.88-0.98, P = 0.003).

CONCLUSIONS

Our analyses suggest age- and geographically associated transmission of DRMs within the HIV genetic network in Mexico City, warranting continuous monitoring and focused interventions.

Genetic clustering analysis for HIV infection among MSM in Nigeria: implications for intervention

BACKGROUND

The HIV epidemic continues to grow among MSM in countries across sub-Saharan Africa including Nigeria. To inform prevention efforts, we used a phylogenetic cluster method to characterize HIV genetic clusters and factors associated with cluster formation among MSM living with HIV in Nigeria.

METHODS

We analyzed HIV-1 pol sequences from 417 MSM living with HIV enrolled in the TRUST/RV368 cohort between 2013 and 2017 in Abuja and Lagos, Nigeria. A genetically linked cluster was defined among participants whose sequences had pairwise genetic distance of 1.5% or less. Binary and multinomial logistic regressions were used to estimate adjusted odds ratios (AORs) and 95% confidence intervals (CIs) for factors associated with HIV genetic cluster membership and size.

RESULTS

Among 417 MSM living with HIV, 153 (36.7%) were genetically linked. Participants with higher viral load (AOR = 1.72 95% CI: 1.04-2.86), no female partners (AOR = 3.66; 95% CI: 1.97-6.08), and self-identified as male sex (compared with self-identified as bigender) (AOR = 3.42; 95% CI: 1.08-10.78) had higher odds of being in a genetic cluster. Compared with unlinked participants, MSM who had high school education (AOR = 23.84; 95% CI: 2.66-213.49), were employed (AOR = 3.41; 95% CI: 1.89-10.70), had bacterial sexually transmitted infections (AOR = 3.98; 95% CI: 0.89-17.22) and were not taking antiretroviral therapy (AOR = 6.61; 95% CI: 2.25-19.37) had higher odds of being in a large cluster (size > 4).

CONCLUSION

Comprehensive HIV prevention packages should include behavioral and biological components, including early diagnosis and treatment of both HIV and bacterial sexually transmitted infections to optimally reduce the risk of HIV transmission and acquisition.

Universal HIV and Birth Cohort HCV Screening in San Diego Emergency Departments

Universal HIV and HCV screening in emergency departments (ED) can reach populations who are less likely to get tested otherwise. The objective of this analysis was to evaluate universal opt-out HIV and HCV screening in two EDs in San Diego. HIV screening for persons aged 13-64 years (excluding persons known to be HIV+ or reporting HIV testing within last 12 months) was implemented using a 4th generation HIV antigen/antibody assay; HCV screening was offered to persons born between 1945 and 1965. Over a period of 16 months, 12,575 individuals were tested for HIV, resulting in 33 (0.26%) new HIV diagnoses, of whom 30 (90%) were successfully linked to care. Universal screening also identified 74 out-of-care for >12-months HIV+ individuals of whom 50 (68%) were successfully relinked to care. Over a one-month period, HCV antibody tests were conducted in 905 individuals with a seropositivity rate of 9.9% (90/905); 61 seropositives who were newly identified or never treated for HCV had HCV RNA testing, of which 31 (51%) resulted positive (3.4% of all participants, including 18 newly identified RNA positives representing 2% of all participants), and 13/31 individuals (42%) were linked to care. The rate of newly diagnosed HCV infections exceeded the rate of newly diagnosed HIV infections by >7-fold, underlining the importance of HCV screening in EDs.

Ethical issues in HIV phylogenetics and molecular epidemiology

PURPOSE OF REVIEW

HIV phylogenetic and molecular epidemiology analyses are increasingly being performed with a goal of improving HIV prevention efforts. However, ethical, legal and social issues are associated with these analyses, and should be considered when performed.

RECENT FINDINGS

Several working groups have recently outlined the major issues surrounding the use of molecular epidemiology for HIV prevention. First, the benefits of HIV molecular epidemiology remain unclear, and further work is needed to quantitatively demonstrate the benefits that can be expected. Second, privacy loss is an important risk, with implications of disclosure varying by the regional legal and social climate. Inferential privacy risks will increase with technological improvements in sequencing and analysis. Third, data sharing, which enhances the utility of the data, may also increase the risk of inferential privacy loss. Mitigation strategies are available to address each of these issues.

SUMMARY

HIV molecular epidemiology for research and public health pose significant ethical issues that continue to evolve with improving technology, increased sampling and a changing legal and social climate. Guidance surrounding these issues needs to be developed for researchers and public health officials in an iterative and region specific manner that accounts for the potential benefits and risks of this technology.

Pilot testing of an online training module about screening for acute HIV infection in adult patients seeking urgent healthcare

BACKGROUND

Acute HIV infection (AHI) is the phase of HIV infection immediately after acquisition, during which many patients develop symptoms and often seek healthcare. However, clinicians in sub-Saharan Africa are not currently taught about AHI.

METHODS

This study pilot-tested a self-directed AHI training module among clinical officers (COs) in coastal Kenya and assessed knowledge gained and challenges to instituting screening. The training module included four domains: AHI definition and importance of AHI recognition; symptoms and screening algorithms; diagnostic strategies; and management. AHI knowledge was assessed before and immediately after training. Participants' ability to utilize an AHI screening algorithm was evaluated with a case-based exercise.

RESULTS

Self-directed training was completed by 45 COs. Pre-test scores were low (median score 35% IQR 30-45%), but improved significantly after training (median post-test score 75%, IQR 70-85%, Wilcoxon signed-rank test p<0.0001). Participants had challenges in understanding the utility and application of a screening algorithm to identify patients for whom AHI testing would be indicated. Knowledge of AHI was poor at baseline, but improved with self-directed learning. Based on these findings, we revised and improved the AHI training module and pre- and post-assessments, which are now freely available online at www.marps-africa.org.

CONCLUSIONS

Guidelines on AHI screening and diagnosis are urgently needed in high HIV transmission areas.

p24 revisited: a landscape review of antigen detection for early HIV diagnosis

: Despite major advances in HIV testing, early detection of infection at the point of care (PoC) remains a key challenge. Although rapid antibody PoC and laboratory-based nucleic acid amplification tests dominate the diagnostics market, the viral capsid protein p24 is recognized as an alternative early virological biomarker of infection. However, the detection of ultra-low levels of p24 at the PoC has proven challenging. Here we review the landscape of p24 diagnostics to identify knowledge gaps and barriers and help shape future research agendas. Five hundred and seventy-four research articles to May 2018 that propose or evaluate diagnostic assays for p24 were identified and reviewed. We give a brief history of diagnostic development, and the utility of p24 as a biomarker in different populations such as infants, the newly infected, those on preexposure prophylaxis and self-testers. We review the performance of commercial p24 assays and consider elements such as immune complex disruption, resource-poor settings, prevalence, and assay antibodies. Emerging and ultrasensitive assays are reviewed and show a number of promising approaches but further translation has been limited. We summarize studies on the health economic benefits of using antigen testing. Finally, we speculate on the future uses of high-performance p24 assays, particularly, if available in self-test format.

High Yield of HIV Testing in Dengue-Like Febrile Illness in Singapore

Where dengue virus infections are endemic, acute febrile illness is often managed as dengue fever (DF) without diagnostic testing. In a prospective study of 140 patients with clinical features of DF, 3 (2.1%) had acute HIV infection (AHI). We recommend testing for AHI in dengue-like febrile illness.

Acute HIV infection detection and immediate treatment estimated to reduce transmission by 89% among men who have sex with men in Bangkok

Introduction: Antiretroviral treatment (ART) reduces HIV transmission. Despite increased ART coverage, incidence remains high among men who have sex with men (MSM) in many places. Acute HIV infection (AHI) is characterized by high viral replication and increased infectiousness. We estimated the feasible reduction in transmission by targeting MSM with AHI for early ART.

Methods: We recruited a cohort of 88 MSM with AHI in Bangkok, Thailand, who initiated ART immediately. A risk calculator based on viral load and reported behaviour, calibrated to Thai epidemiological data, was applied to estimate the number of onwards transmissions. This was compared with the expected number without early interventions.

Results: Forty of the MSM were in 4th-generation AHI stages 1 and 2 (4thG stage 1, HIV nucleic acid testing (NAT)+/4thG immunoassay (IA)-/3rdG IA–; 4thG stage 2, NAT+/4thG IA+/3rdG IA–) while 48 tested positive on third-generation IA but had negative or indeterminate western blot (4thG stage 3). Mean plasma HIV RNA was 5.62 log¹⁰ copies/ml. Any condomless sex in the four months preceding the study was reported by 83.7%, but decreased to 21.2% by 24 weeks on ART. After ART, 48/88 (54.6%) attained HIV RNA <50 copies/ml by week 8, increasing to 78/87 (89.7%), and 64/66 (97%) at weeks 24 and 48, respectively. The estimated number of onwards transmissions in the first year of infection would have been 27.3 (95% credible interval: 21.7–35.3) with no intervention, 8.3 (6.4–11.2) with post-diagnosis behaviour change only, 5.9 (4.4–7.9) with viral load reduction only and 3.1 (2.4–4.3) with both. The latter was associated with an 88.7% (83.8–91.1%) reduction in transmission.

Conclusions: Disproportionate HIV transmission occurs during AHI. Diagnosis of AHI with early ART initiation can substantially reduce onwards transmission.

Transmission network characteristics based on env and gag sequences from MSM during acute HIV-1 infection in Beijing, China

Molecular epidemiology can be used to identify human immunodeficiency virus (HIV) transmission clusters, usually using pol sequence for analysis. In the present study, we explored appropriate parameters to construct a simple network using HIV env and gag sequences instead of pol sequences for constructing a phylogenetic tree and a genetic transmission subnetwork, which were used to identify individuals with many potential transmission links and to explore the evolutionary dynamics of the virus among men who have sex with men (MSM) in Beijing. We investigated 70 acute HIV-1 infections, which consisted of HIV-1 subtype B (15.71%), the circulating recombinant forms CRF01_AE (47.14%), CRF07_BC (21.43%), CRF55_01B (1.43%), and CRF65_cpx (4.29%), and an unknown subtype (10.00%). By exploring the similarities and differences among HIV env, gag and pol sequences in describing the dynamics of the HIV-1 CRF01_AE transmission subnetwork among Beijing MSM, we found that four key points of the env sequences (strains E-2011_BJ.CY_16014, E-2011_BJ.FT_16017, E-2011_BJ.TZ_16064, and E-2011_BJ.XW_16035) contained more transmission information than gag sequences (three key points: strains G-2011_BJ.CY_16014, G-2011_BJ.FT_16017, and G-2011_BJ.XW_16035) and pol sequences (two key points: strains P-2011_BJ.CY_16014 and P-2011_BJ.XW_16035). Although the env and gag sequence results were similar to pol sequences in describing the dynamics of the HIV-1 CRF01_AE transmission subnetwork, we were able to obtain more precise information, allowing identification of key points of subnetwork expansion, based on HIV env and gag sequences instead of pol sequences. Taken together, the key points we found will improve our current understanding of how HIV spreads between MSM populations in Beijing and help to better target preventative interventions for promoting public health.

Spatiotemporal dynamics of HIV-1 transmission in France (1999-2014) and impact of targeted prevention strategies

Background

Characterizing HIV-1 transmission networks can be important in understanding the evolutionary patterns and geospatial spread of the epidemic. We reconstructed the broad molecular epidemiology of HIV from individuals with primary HIV-1 infection (PHI) enrolled in France in the ANRS PRIMO C06 cohort over 15 years.

Results

Sociodemographic, geographic, clinical, biological and pol sequence data from 1356 patients were collected between 1999 and 2014. Network analysis was performed to infer genetic relationships, i.e. clusters of transmission, between HIV-1 sequences. Bayesian coalescent-based methods were used to examine the temporal and spatial dynamics of identified clusters from different regions in France. We also evaluated the use of network information to target prevention efforts. Participants were mostly Caucasian (85.9%) and men (86.7%) who reported sex with men (MSM, 71.4%). Overall, 387 individuals (28.5%) were involved in clusters: 156 patients (11.5%) in 78 dyads and 231 participants (17%) in 42 larger clusters (median size: 4, range 3–41). Compared to individuals with single PHI (n = 969), those in clusters were more frequently men (95.9 vs 83%, p < 0.01), MSM (85.8 vs 65.6%, p < 0.01) and infected with CRF02_AG (20.4 vs 13.4%, p < 0.01). Reconstruction of viral migrations across time suggests that Paris area was the major hub of dissemination of both subtype B and CRF02_AG epidemics. By targeting clustering individuals belonging to the identified active transmission network before 2010, 60 of the 143 onward transmissions could have been prevented.

Conclusion

These analyses support the hypothesis of a recent and rapid rise of CRF02_AG within the French HIV-1 epidemic among MSM. Combined with a short turnaround time for sample processing, targeting prevention efforts based on phylogenetic monitoring may be an efficient way to deliver prevention interventions but would require near real time targeted interventions on the identified index cases and their partners.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-017-0339-4) contains supplementary material, which is available to authorized users.

HIV surveillance combining an assay for identification of very recent infection and phylogenetic analyses on dried spots

BACKGROUND

Transmitted/founder viruses isolated at the early stage of infection are indicators of the variants that are spreading within a population. The French reporting system for new HIV diagnoses is linked to a virological surveillance using dried serum spots.

METHODS

We combined an immunoassay for very recent infection (less than 31 days) to a phylogenetic analysis of transmitted/founder viruses and sociodemographic information to analyze the dynamics of the HIV-1 epidemic during a 3-year period. Bayesian coalescent-based methods were used to explore the temporal and spatial dynamics of the identified clusters.

RESULTS

Of 17 010 dried serum spots collected, 549 very recent infections were identified for which both env sequences and sociodemographic data were available. Non-B transmitted/founder viruses were found in 196 cases (35.7%), belonging to six subtypes and seven circulating recombinant forms. Forty-three dyads/clusters were identified (range 2-11 cases), including 107 individuals (19.5%), mainly MSM. The largest cluster involved MSM infected by a CRF02_AG variant. Reconstruction of viral migrations across time suggests that Paris was the major hub of dissemination.

CONCLUSION

The study shows the feasibility of the surveillance of the HIV epidemic using this methodology. The observation of actively growing spatiotemporal clusters allows identification of specific networks that may be targets for intervention.

Concurrency and HIV transmission network characteristics among MSM with recent HIV infection

OBJECTIVE

Sexual partner concurrency is common among MSM and may increase the probability of HIV transmission during recent (acute or early) infection. We examined the relationship between concurrency and HIV transmission network characteristics (proxies for HIV transmission) among MSM with recent HIV infection.

DESIGN

Observational study integrating behavioral, clinical, and molecular epidemiology.

METHODS

We inferred a partial HIV transmission network using 986 HIV-1 pol sequences obtained from HIV-infected individuals in San Diego, California (1996-2015). We further analyzed data from 285 recently HIV-infected MSM in the network who provided information on up to three sexual partners in the past 3 months, including the timing of intercourse with each partner. Concurrency was defined as sexual partners overlapping in time. Logistic and negative binomial regressions were used to investigate the link between concurrency and HIV transmission network characteristics (i.e. clustering and degree or number of connections to others in the network) among these MSM.

RESULTS

Of recently HIV-infected MSM (n = 285), 54% reported concurrent partnerships and 54% were connected by at least one putative transmission link to others (i.e. clustered) in the network (median degree = 1.0; interquartile range: 0.0-3.0). Concurrency was positively associated with HIV transmission network clustering (adjusted odds ratio = 1.83, 95% confidence interval: 1.08, 3.10) and degree (adjusted incidence rate ratio = 1.48, 95% confidence interval: 1.02, 2.15).

CONCLUSION

Our findings provide empirical evidence consistent with the hypothesis that concurrency facilitates HIV transmission during recent infection. Interventions to mitigate the impact of concurrency on HIV transmission may help curb the HIV epidemic among MSM.