Phylogenetic evidence of HIV-1 transmission linkage between two men who have sex with men

Abstract Background In China, an HIV-infected man (complainant; P2) alleged that another man (defendant; P1) had unlawfully infected him with HIV through unprotected homosexual contact in 2018. Methods We employed epidemiological, serological and phylogenetic analyses to investigate the transmission linkage between two men who have sex with men (MSM). Partial segments of three HIV-1 gene regions (gag, pol, and env) were amplified and sequenced by cloning. Maximum-likelihood (ML) and Bayesian methods were used to determine the direction and estimate the timing of transmission. Local control sequences and database control sequences were also used in the phylogenetic analysis. Results It indicated that P2 underwent HIV seroconversion after P1 was diagnosed as HIV positive. The time to the most recent common ancestor (tMRCA) estimates consistently showed that P1 most likely became HIV-1 infected at an earlier date than P2. P1 and P2 were infected with the same HIV-1 CRF01_AE subtype according to segments of all three gene regions (gag, pol, and env). All three genetic regions of P1 have been subject to more potential selective forces than those of P2, indicating a longer evolutionary history. Bayesian and ML trees showed similar paraphyletic-monophyletic topologies of gag and env, with the virus from P1 located at the root, which supported a P1-to-P2 transmission direction. Conclusions Phylogenetic investigations can elucidate HIV transmission linkage and might empower its use in the opposition of the intentional transmission of HIV-1 as a forensic tool.

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Phylogenetic and genetic characterization of Treponema pallidum strains from syphilis patients in Japan by whole-genome sequence analysis from global perspectives

Scientific Reports ◽

10.1038/s41598-021-82337-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Shingo Nishiki ◽

Kenichi Lee ◽

Mizue Kanai ◽

Shu-ichi Nakayama ◽

Makoto Ohnishi

Keyword(s):

Genetic Difference ◽

Phylogenetic Analyses ◽

Treponema Pallidum ◽

Whole Genome Sequence ◽

Epidemiological Surveillance ◽

Recent Common Ancestor ◽

Whole Genome ◽

Global Perspectives ◽

Most Recent Common Ancestor ◽

Sex With Men

AbstractJapan has had a substantial increase in syphilis cases since 2013. However, research on the genomic features of the Treponema pallidum subspecies pallidum (TPA) strains from these cases has been limited. Here, we elucidated the genetic variations and relationships between TPA strains in Japan (detected between 2014 and 2018) and other countries by whole-genome sequencing and phylogenetic analyses, including syphilis epidemiological surveillance data and information on patient sexual orientation. Seventeen of the 20 strains in Japan were SS14- and the remaining 3 were Nichols-lineage. Sixteen of the 17 SS14-lineage strains were classified into previously reported Sub-lineage 1B. Sub-lineage 1B strains in Japan have formed distinct sub-clusters of strains from heterosexuals and strains from men who have sex with men. These strains were closely related to reported TPA strains in China, forming an East-Asian cluster. However, those strains in these countries evolved independently after diverging from their most recent common ancestor and expanded their genetic diversity during the time of syphilis outbreak in each country. The genetic difference between the TPA strains in these countries was characterized by single-nucleotide-polymorphism analyses of their penicillin binding protein genes. Taken together, our results elucidated the detailed phylogenetic features and transmission networks of syphilis.

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Evaluation of HIV Transmission Clusters among Natives and Foreigners Living in Italy

Viruses ◽

10.3390/v12080791 ◽

2020 ◽

Vol 12 (8) ◽

pp. 791 ◽

Cited By ~ 2

Author(s):

Lavinia Fabeni ◽

Maria Mercedes Santoro ◽

Patrizia Lorenzini ◽

Stefano Rusconi ◽

Nicola Gianotti ◽

...

Keyword(s):

Hiv Transmission ◽

Phylogenetic Analyses ◽

Hiv Infections ◽

Public Health Response ◽

Health Response ◽

Drug Naïve ◽

Recent Diagnosis ◽

Sex With Men ◽

Italian Origin ◽

Hiv 1

We aimed at evaluating the characteristics of HIV-1 molecular transmission clusters (MTCs) among natives and migrants living in Italy, diagnosed between 1998 and 2018. Phylogenetic analyses were performed on HIV-1 polymerase (pol) sequences to characterise subtypes and identify MTCs, divided into small (SMTCs, 2–3 sequences), medium (MMTCs, 4–9 sequences) and large (LMTCs, ≥10 sequences). Among 3499 drug-naïve individuals enrolled in the Italian Cohort Naive Antiretroviral (ICONA) cohort (2804 natives; 695 migrants), 726 (20.8%; 644 natives, 82 migrants) were involved in 228 MTCs (6 LMTCs, 36 MMTCs, 186 SMTCs). Migrants contributed 14.4% to SMTCs, 7.6% to MMTCs and 7.1% to LMTCs, respectively. HIV-1 non-B subtypes were found in 51 MTCs; noteworthy was that non-B infections involved in MTCs were more commonly found in natives (n = 47) than in migrants (n = 4). Factors such as Italian origin, being men who have sex with men (MSM), younger age, more recent diagnosis and a higher CD4 count were significantly associated with MTCs. Our findings show that HIV-1 clustering transmission among newly diagnosed individuals living in Italy is prevalently driven by natives, mainly MSM, with a more recent diagnosis and frequently infected with HIV-1 non-B subtypes. These results can contribute to monitoring of the HIV epidemic and guiding the public health response to prevent new HIV infections.

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Identification of a New HIV-1 BC Intersubtype Circulating Recombinant Form (CRF108_BC) in Spain

Viruses ◽

10.3390/v13010093 ◽

2021 ◽

Vol 13 (1) ◽

pp. 93

Author(s):

Javier E. Cañada ◽

Elena Delgado ◽

Horacio Gil ◽

Mónica Sánchez ◽

Sonia Benito ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Basque Country ◽

Recent Common Ancestor ◽

Subtype C ◽

Northern Spain ◽

Most Recent Common Ancestor ◽

Phylogenetic Cluster ◽

Subtype B ◽

Definition Of ◽

Hiv 1

The extraordinary genetic variability of human immunodeficiency virus type 1 (HIV-1) group M has led to the identification of 10 subtypes, 102 circulating recombinant forms (CRFs) and numerous unique recombinant forms. Among CRFs, 11 derived from subtypes B and C have been identified in China, Brazil, and Italy. Here we identify a new HIV-1 CRF_BC in Northern Spain. Originally, a phylogenetic cluster of 15 viruses of subtype C in protease-reverse transcriptase was identified in an HIV-1 molecular surveillance study in Spain, most of them from individuals from the Basque Country and heterosexually transmitted. Analyses of near full-length genome sequences from six viruses from three cities revealed that they were BC recombinant with coincident mosaic structures different from known CRFs. This allowed the definition of a new HIV-1 CRF designated CRF108_BC, whose genome is predominantly of subtype C, with four short subtype B fragments. Phylogenetic analyses with database sequences supported a Brazilian ancestry of the parental subtype C strain. Coalescent Bayesian analyses estimated the most recent common ancestor of CRF108_BC in the city of Vitoria, Basque Country, around 2000. CRF108_BC is the first CRF_BC identified in Spain and the second in Europe, after CRF60_BC, both phylogenetically related to Brazilian subtype C strains.

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Identification of CRF66_BF, a new HIV-1 circulating recombinant form of South American origin

10.1101/2021.09.14.460288 ◽

2021 ◽

Author(s):

Joan Bacque ◽

Elena Delgado ◽

Sonia Benito ◽

Maria Moreno-Lorenzo ◽

Vanessa Montero ◽

...

Keyword(s):

Phylogenetic Trees ◽

Recent Common Ancestor ◽

South American ◽

Most Recent Common Ancestor ◽

Phylogenetic Cluster ◽

Subtype B ◽

Sex With Men ◽

Full Length Genome ◽

South American Origin ◽

Hiv 1

Circulating recombinant forms (CRFs) are important components of the HIV-1 pandemic. Among 108 reported in the literature, 17 are BF1 intersubtype recombinant, most of which are of South American origin. Among these, all 5 identified in the Southern Cone and neighboring countries, except Brazil, derive from a common recombinant ancestor related to CRF12_BF, which circulates widely in Argentina, as deduced from coincident breakpoints and clustering in phylogenetic trees. In a HIV-1 molecular epidemiological study in Spain, we identified a phylogenetic cluster of 20 samples from 3 separate regions which were of F1 subsubtype, related to the Brazilian strain, in protease-reverse transcriptase (Pr-RT) and of subtype B in integrase. Remarkably, 14 individuals from this cluster (designated BF9) were Paraguayans and only 4 were native Spaniards. HIV-1 transmission was predominantly heterosexual, except for a subcluster of 6 individuals, 5 of which were men who have sex with men. Ten additional database sequences, from Argentina (n=4), Spain (n=3), Paraguay (n=1), Brazil (n=1), and Italy (n=1), branched within the BF9 cluster. To determine whether it represents a new CRF, near full-length genome (NFLG) sequences were obtained for 6 viruses from 3 Spanish regions. Bootscan analyses showed a coincident BF1 recombinant structure, with 5 breakpoints, located in p17gag, integrase, gp120, gp41-rev overlap, and nef, which was identical to that of two BF1 recombinant viruses from Paraguay previously sequenced in NFLGs. Interestingly, none of the breakpoints coincided with those of CRF12_BF. In a maximum likelihood phylogenetic tree, all 8 NFLG sequences grouped in a strongly supported clade segregating from previously identified CRFs and from the CRF12_BF family clade. These results allow us to identify a new HIV-1 CRF, designated CRF66_BF. Through a Bayesian coalescent analysis, the most recent common ancestor of CRF66_BF was estimated around 1984 in South America, either in Paraguay or Argentina. Among Pr-RT sequences obtained by us from HIV-1-infected Paraguayans living in Spain, 14 (20.9%) of 67 were of CRF66_BF, suggesting that CRF66_BF may be one of the major HIV-1 genetic forms circulating in Paraguay. CRF66_BF is the first reported non-Brazilian South American HIV-1 CRF_BF unrelated to CRF12_BF

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Identification of CRF66_BF, a New HIV-1 Circulating Recombinant Form of South American Origin

Frontiers in Microbiology ◽

10.3389/fmicb.2021.774386 ◽

2021 ◽

Vol 12 ◽

Author(s):

Joan Bacqué ◽

Elena Delgado ◽

Sonia Benito ◽

María Moreno-Lorenzo ◽

Vanessa Montero ◽

...

Keyword(s):

Phylogenetic Trees ◽

Recent Common Ancestor ◽

South American ◽

Most Recent Common Ancestor ◽

Phylogenetic Cluster ◽

Subtype B ◽

Sex With Men ◽

Full Length Genome ◽

South American Origin ◽

Hiv 1

Circulating recombinant forms (CRFs) are important components of the HIV-1 pandemic. Among 110 reported in the literature, 17 are BF1 intersubtype recombinant, most of which are of South American origin. Among these, all 5 identified in the Southern Cone and neighboring countries, except Brazil, derive from a common recombinant ancestor related to CRF12_BF, which circulates widely in Argentina, as deduced from coincident breakpoints and clustering in phylogenetic trees. In a HIV-1 molecular epidemiological study in Spain, we identified a phylogenetic cluster of 20 samples from 3 separate regions which were of F1 subsubtype, related to the Brazilian strain, in protease-reverse transcriptase (Pr-RT) and of subtype B in integrase. Remarkably, 14 individuals from this cluster (designated BF9) were Paraguayans and only 4 were native Spaniards. HIV-1 transmission was predominantly heterosexual, except for a subcluster of 6 individuals, 5 of which were men who have sex with men. Ten additional database sequences, from Argentina (n = 4), Spain (n = 3), Paraguay (n = 1), Brazil (n = 1), and Italy (n = 1), branched within the BF9 cluster. To determine whether it represents a new CRF, near full-length genome (NFLG) sequences were obtained for 6 viruses from 3 Spanish regions. Bootscan analyses showed a coincident BF1 recombinant structure, with 5 breakpoints, located in p17gag, integrase, gp120, gp41-rev overlap, and nef, which was identical to that of two BF1 recombinant viruses from Paraguay previously sequenced in NFLGs. Interestingly, none of the breakpoints coincided with those of CRF12_BF. In a maximum likelihood phylogenetic tree, all 8 NFLG sequences grouped in a strongly supported clade segregating from previously identified CRFs and from the CRF12_BF “family” clade. These results allow us to identify a new HIV-1 CRF, designated CRF66_BF. Through a Bayesian coalescent analysis, the most recent common ancestor of CRF66_BF was estimated around 1984 in South America, either in Paraguay or Argentina. Among Pr-RT sequences obtained by us from HIV-1-infected Paraguayans living in Spain, 14 (20.9%) of 67 were of CRF66_BF, suggesting that CRF66_BF may be one of the major HIV-1 genetic forms circulating in Paraguay. CRF66_BF is the first reported non-Brazilian South American HIV-1 CRF_BF unrelated to CRF12_BF.

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Nation-Wide Viral Sequence Analysis of HIV-1 Subtype B Epidemic in 2003–2012 Revealed a Contribution of Men Who Have Sex With Men to the Transmission Cluster Formation and Growth in Japan

Frontiers in Reproductive Health ◽

10.3389/frph.2020.531212 ◽

2020 ◽

Vol 2 ◽

Author(s):

Teiichiro Shiino ◽

Atsuko Hachiya ◽

Junko Hattori ◽

Wataru Sugiura ◽

Kazuhisa Yoshimura

Keyword(s):

Recent Common Ancestor ◽

Bayesian Posterior Probability ◽

Newly Diagnosed ◽

Surveillance Network ◽

Relative Population ◽

Most Recent Common Ancestor ◽

Subtype B ◽

Geographical Regions ◽

Sex With Men ◽

Hiv 1

Background: To better understand the epidemiology of human immunodeficiency virus type 1 (HIV-1) subtype B transmission in Japan, phylodynamic analysis of viral pol sequences was conducted on individuals newly diagnosed as HIV-1 seropositive.Methodology: A total of 5,018 patients newly diagnosed with HIV-1 infection and registered in the Japanese Drug Resistance HIV Surveillance Network from 2003 to 2012 were enrolled in the analysis. Using the protease-reverse transcriptase nucleotide sequences, their subtypes were determined, and phylogenetic relationships among subtype B sequences were inferred using three different methods: distance-matrix, maximum likelihood, and Bayesian Markov chain Monte Carlo. Domestically spread transmission clusters (dTCs) were identified based on the following criteria: >95% in interior branch test, >95% in Bayesian posterior probability and <10% in depth-first searches for sub-tree partitions. The association between dTC affiliation and individuals' demographics was analyzed using univariate and multivariate analyses.Results: Among the cases enrolled in the analysis, 4,398 (87.6%) were classified as subtype B. Many of them were Japanese men who had sex with men (MSM), and 3,708 (84.3%) belonged to any of 312 dTCs. Among these dTCs, 243 (77.9%) were small clusters with <10 individuals, and the largest cluster consisted of 256 individuals. Most dTCs had median time of the most recent common ancestor between 1995 and 2005, suggesting that subtype B infection was spread among MSMs in the second half of the 1990s. Interestingly, many dTCs occurred within geographical regions. Comparing with singleton cases, TCs included more MSM, young person, and individuals with high CD4+ T-cell count at the first consultation. Furthermore, dTC size was significantly correlated with gender, age, transmission risks, recent diagnosis and relative population size of the region mainly distributed.Conclusions: Our study clarified that major key population of HIV-1 subtype B epidemic in Japan is local MSM groups. The study suggests that HIV-1 subtype B spread via episodic introductions into the local MSM groups, some of the viruses spread to multiple regions. Many cases in dTC were diagnosed during the early phase of infection, suggesting their awareness to HIV risks.

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First complete-genome documentation of HIV-1 intersubtype superinfection with transmissions of diverse recombinants over time to five recipients

PLoS Pathogens ◽

10.1371/journal.ppat.1009258 ◽

2021 ◽

Vol 17 (2) ◽

pp. e1009258

Author(s):

Yang Gao ◽

Shan He ◽

Wen Tian ◽

Dan Li ◽

Minghui An ◽

...

Keyword(s):

Sexual Behaviors ◽

Phylogenetic Trees ◽

Evolutionary Relationship ◽

Recent Common Ancestor ◽

Monophyletic Cluster ◽

Most Recent Common Ancestor ◽

Immunodeficiency Virus ◽

Sex With Men ◽

Full Length Genome ◽

Hiv 1

Human immunodeficiency virus type 1 (HIV-1) recombinants in the world are believed to be generated through recombination between distinct HIV-1 strains among coinfection or superinfection cases. However, direct evidence to support transmission of HIV-1 recombinants from a coinfected/superinfected donor to putative recipient is lacking. Here, we report on the origin and evolutionary relationship between a set of recombinants from a CRF01_AE/CRF07_BC superinfected putative donor and diverse CRF01_AE/CRF07_BC recombinants from five putative recipients. Interviews on sociodemographic characteristics and sexual behaviors for these six HIV-1-infected men who have sex with men showed that they had similar ways of partner seeking: online dating sites and social circles. Phylogenetic and recombination analyses demonstrated that the near-full-length genome sequences from six patients formed a monophyletic cluster different from known HIV-1 genotypes in maximum likelihood phylogenetic trees, were all composed of CRF01_AE and CRF07_BC fragments with two common breakpoints on env, and shared 4–7 breakpoints with each other. Moreover, 3’ half-genomes of recombinant strains from five recipients had identical/similar recombinant structures with strains at longitudinal samples from the superinfected donor. Recombinants from the donor were paraphyletic, whereas five recipients were monophyletic or polyphyletic in the maximum clade credibility tree. Bayesian analyses confirmed that the estimated time to the most recent common ancestor (tMRCA) of CRF01_AE and CRF07_BC strains of the donor was 2009.2 and 2010.7, respectively, and all were earlier than the emergence of recombinants from five recipients. Our results demonstrated that the closely related unique recombinant forms of HIV-1 might be the descendent of a series of recombinants generated gradually in a superinfected patient. This finding highlights the importance of early initiation of antiretroviral therapy as well as tracing and testing of partners in patients with multiple HIV-1 infection.

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The reporting of the mode of transmission among HIV-positive men who have sex with men in Lviv oblast, Ukraine, 2014-2018

The Journal of Infection in Developing Countries ◽

10.3855/jidc.11967 ◽

2020 ◽

Vol 14 (11.1) ◽

pp. 122S-127S

Author(s):

Maryana Sluzhynska ◽

Olga Denisiuk ◽

Ruzanna Grigoryan ◽

Yulia Sereda ◽

Gennadiy Slabkiy ◽

...

Keyword(s):

Urban Areas ◽

Hiv Transmission ◽

Cross Sectional Study ◽

Medical Doctor ◽

Hiv Care ◽

Hiv Positive ◽

Cross Sectional ◽

Aids Epidemic ◽

Mode Of Transmission ◽

Sex With Men

Introduction: Men who have sex with men (MSM) are one of the key populations driving HIV/AIDS epidemic globally. To date, MSM is the only population in Ukraine where the prevalence and incidence of HIV is increasing. As HIV-positive MSM might feel uncomfortable to report homosexual intercourses as a possible mode of transmission (MoT) of HIV, they prefer being registered as patients with heterosexual or non-defined MoT. This study aimed to calculate the proportion of misclassified MoT among HIV-positive MSM registered in Lviv oblast, Ukraine, during 2014-2018. Methodology: Cross-sectional study with 127 HIV-positive MSM patients from Lviv region for the period of 2014-2018. Results: Out of 127 HIV-positive MSM included in the study, 110 (86.6%) were from urban areas. In addition, 52 patients (40.9%) were diagnosed with stage 1 HIV, 16 (12.6%) – stage 2, 19 (15%) – stage 3, and 36 (28.3%) – stage 4. CD4 count < 200 cells/μL was found in 35 (27.6%) patients. Mean time from registration to antiretroviral therapy initiation was 80 days. During the first visit to medical doctor out of those 48 patients who had previously reported “other modes” of HIV transmission, 33 patients (68.7%) disclosed homosexual MoT of HIV. The remaining 15 (31.3%) patients disclosed their homosexual MoT of HIV later – during their regular follow-up visits to the doctor. Conclusion: Special measures are needed to improve the reporting of homosexual MoT which can potentially strengthen the HIV care among MSM.

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A FOUNDER EFFECT LED EARLY SARS-COV-2 TRANSMISSION IN SPAIN

Journal of Virology ◽

10.1128/jvi.01583-20 ◽

2020 ◽

Cited By ~ 1

Author(s):

Francisco Díez-Fuertes ◽

María Iglesias-Caballero ◽

Javier García Pérez ◽

Sara Monzón ◽

Pilar Jiménez ◽

...

Keyword(s):

Founder Effect ◽

Phylogenetic Analyses ◽

Protein A ◽

Spike Protein ◽

Recent Common Ancestor ◽

Whole Genome ◽

Whole Genome Analysis ◽

Most Recent Common Ancestor ◽

Fitness Advantage

SARS-CoV-2 whole-genome analysis has identified five large clades worldwide, emerged in 2019 (19A and 19B) and in 2020 (20A, 20B and 20C). This study aims to analyze the diffusion of SARS-CoV-2 in Spain using maximum likelihood phylogenetic and Bayesian phylodynamic analyses. The most recent common ancestor (MRCA) of the SARS-CoV-2 pandemic was estimated in Wuhan, China, around November 24, 2019. Phylogenetic analyses of the first 12,511 SARS-CoV-2 whole genome sequences obtained worldwide, including 290 from 11 different regions of Spain, revealed 62 independent introductions of the virus in the country. Most sequences from Spain were distributed in clades characterized by D614G substitution in S gene (20A, 20B and 20C) and L84S substitution in ORF8 (19B) with 163 and 118 sequences, respectively, with the remaining sequences branching in 19A. A total of 110 (38%) sequences from Spain grouped in four different monophyletic clusters of 20A clade (20A-Sp1 and 20A-Sp2) and 19B clade (19B-Sp1 and 19B-Sp2) along with sequences from 29 countries worldwide. The MRCA of 19A-Sp1, 20A-Sp1, 19A-Sp2 and 20A-Sp2 clusters were estimated in Spain around January 21 and 29, and February 6 and 17, 2020, respectively. The prevalence of 19B clade in Spain (40%) was by far higher than in any other European country during the first weeks of the epidemic, probably by a founder effect. However, this variant was replaced by G614-bearing viruses in April. In vitro assays showed an enhanced infectivity of pseudotyped virions displaying G614 substitution compared with D614, suggesting a fitness advantage of D614G. IMPORTANCE Multiple SARS-CoV-2 introductions have been detected in Spain and at least four resulted in the emergence of locally transmitted clusters originated not later than mid-February, with further dissemination to many other countries around the world and a few weeks before the explosion of COVID-19 cases detected in Spain during the first week of March. The majority of the earliest variants detected in Spain branched in 19B clade (D614 viruses), which was the most prevalent clade during the first weeks of March, pointing to a founder effect. However, from mid-March to June, 2020, G614-bearing viruses (20A, 20B and 20C clades) overcame D614 variants in Spain, probably as a consequence of an evolutionary advantage of this substitution in the spike protein. A higher infectivity of G614-bearing viruses compared to D614 variants was detected, suggesting that this substitution in SARS-CoV-2 spike protein could be behind the variant shift observed in Spain.

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Superimposing incident sexually transmitted infections on HIV phylogram to investigate possible misclassification of men who have sex with men as heterosexuals in a cohort in Antwerp, Belgium

International Journal of STD & AIDS ◽

10.1177/0956462418821752 ◽

2019 ◽

Vol 30 (5) ◽

pp. 486-495

Author(s):

Kara K Osbak ◽

Conor J Meehan ◽

Sergio G Ribas ◽

Leo Heyndrickx ◽

Kevin K Ariën ◽

...

Keyword(s):

Sexually Transmitted Infections ◽

Sexual Behaviour ◽

Hiv Transmission ◽

Phylogenetic Analyses ◽

Laboratory Data ◽

Risk Groups ◽

Transmission Risk ◽

Sexually Transmitted ◽

Sex With Men ◽

Hiv Transmission Risk

In this study, we assessed if the superimposition of incident sexually transmitted infections (STIs) on HIV phylogenetic analyses could reveal possible sexual behaviour misclassifications in our HIV-infected population. HIV-1 sequences collected between 1997 and 2014 from 1169 individuals attending a HIV clinic in Antwerp, Belgium were analysed to infer a partial HIV transmission network. Individual demographic, clinical and laboratory data collected during routine HIV follow-up were used to compare clustered and non-clustered individuals using logistic regression analyses. In total, 438 (37.5%) individuals were identified in 136 clusters, including 76 transmission pairs and 60 clusters consisting of three or more individuals. Individuals in a cluster were more likely to have a history of syphilis, Chlamydia and/or gonorrhoea (P < 0.05); however, when analyses were stratified by HIV transmission risk groups (heterosexual and men who have sex with men [MSM]), this association only remained significant for heterosexuals with syphilis (P = 0.001). Under closer scrutiny, this association was driven by six heterosexual men who were located in six almost exclusively MSM clusters. A parsimonious conclusion is that these six individuals were potentially misclassified as heterosexual. Improving the accuracy of sexual behaviour reporting could improve care.

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