Publications by Year: 2020

2020
Uusküla A, Vickerman P, Raag M, Walker J, Paraskevis D, Eritsyan K, Sypsa V, Lioznov D, Avi R, Des Jarlais D. Presenting a conceptual framework for an HIV prevention and care continuum and assessing the feasibility of empirical measurement in Estonia: A case study. PLoS OnePLoS OnePLoS One. 2020;15:e0240224.Abstract
OBJECTIVE: We aim to show the feasibility of using an integrated prevention and care continuum (PCC) model as a complete and improved tool for HIV control measurement and programming. Alignment of prevention and care continua is essential to further improve health outcomes and minimize HIV transmission risk. DESIGN: Cross-sectional study. METHODS: Data from 977 persons who inject drugs (PWID) collected in 2011-2016 in Tallinn, Estonia, were used to construct an HIV PCC for PWID, stratified by risk for acquiring or transmitting HIV infection and by coverage of combined interventions. We also estimated the average protective effect of current levels of intervention provision. RESULTS: 74.4%, 20.3% and 35.2% of PWID were currently using needle and syringe programmes (NSP), drug treatment and HIV testing, respectively. 51.1% of current PWID were HIV seropositive and of those 62.5% were currently on ART and 19.0% were virally suppressed. Across the PCC, individuals moved between categories of being aware and ever using drug treatment (resulting in -50% "leakage"); from ever having used to currently using drug treatment (-59%); between "ever testing" and "current (continuous) testing" (-62%); and from self-reported antiretroviral therapy (ART) adherence to viral suppression (-70%). Use of prevention services was higher among those at risk of transmission (HIV positive). The overall reduction in acquisition risk among HIV-negative PWID was 77.7% (95% CrI 67.8-84.5%), estimated by the modelled protective effects of current levels of NSP, drug treatment and ART compared to none of these services. CONCLUSIONS: Our findings suggest that developing a cohesive model for HIV prevention and treatment is feasible and reflects the bi-directional relationships between prevention and care. The integrated continuum model indicates the major factors which may predict the epidemic course and control response.
Vasylyeva TI, Zarebski A, Smyrnov P, Williams LD, Korobchuk A, Liulchuk M, Zadorozhna V, Nikolopoulos G, Paraskevis D, Schneider J, et al. Phylodynamics Helps to Evaluate the Impact of an HIV Prevention Intervention. VirusesVirusesViruses. 2020;12.Abstract
Assessment of the long-term population-level effects of HIV interventions is an ongoing public health challenge. Following the implementation of a Transmission Reduction Intervention Project (TRIP) in Odessa, Ukraine, in 2013-2016, we obtained HIV pol gene sequences and used phylogenetics to identify HIV transmission clusters. We further applied the birth-death skyline model to the sequences from Odessa (n = 275) and Kyiv (n = 92) in order to estimate changes in the epidemic's effective reproductive number (R(e)) and rate of becoming uninfectious (δ). We identified 12 transmission clusters in Odessa; phylogenetic clustering was correlated with younger age and higher average viral load at the time of sampling. Estimated R(e) were similar in Odessa and Kyiv before the initiation of TRIP; R(e) started to decline in 2013 and is now below R(e) = 1 in Odessa (R(e) = 0.4, 95%HPD 0.06-0.75), but not in Kyiv (R(e) = 2.3, 95%HPD 0.2-5.4). Similarly, estimates of δ increased in Odessa after the initiation of TRIP. Given that both cities shared the same HIV prevention programs in 2013-2019, apart from TRIP, the observed changes in transmission parameters are likely attributable to the TRIP intervention. We propose that molecular epidemiology analysis can be used as a post-intervention effectiveness assessment tool.
Psichogiou M, Karabinis A, Pavlopoulou ID, Basoulis D, Petsios K, Roussos S, Pratikaki M, Jahaj E, Protopapas K, Leontis K, et al. Antibodies against SARS-CoV-2 among health care workers in a country with low burden of COVID-19. PLoS OnePLoS OnePLoS One. 2020;15:e0243025.Abstract
INTRODUCTION: Greece is a country with limited spread of SARS-CoV-2 and cumulative infection attack rate of 0.12% (95% CI 0.06-0.26). Health care workers (HCWs) are a well-recognized risk group for COVID-19. The study aimed to estimate the seroprevalence of antibodies to SARS-CoV-2 in a nosocomial setting and assess potential risk factors. METHODS: HCWs from two hospitals participated in the study. Hospital-1 was a tertiary university affiliated center, involved in the care of COVID-19 patients while hospital-2 was a tertiary specialized cardiac surgery center not involved in the care of these patients. A validated, CE, rapid, IgM/IgG antibody point-of-care test was used. Comparative performance with a reference globally available assay was assessed. RESULTS: 1,495 individuals consented to participate (response rate 77%). The anti-SARS-CoV-2 weighted prevalence was 1.26% (95% CI 0.43, 3.26) overall and 0.53% (95% CI 0.06, 2.78) and 2.70% (95% CI 0.57, 9.19) in hospital-1 and hospital-2, respectively although the study was underpowered to detect statistically significant differences. The overall, hospital-1, and hospital-2 seroprevalence was 10, 4 and 22 times higher than the estimated infection attack rate in general population, respectively. Suboptimal use of personal protective equipment was noted in both hospitals. CONCLUSIONS: These data have implications for the preparedness of a second wave of COVID-19 epidemic, given the low burden of SARS-CoV-2 infection rate, in concordance with national projections.
Surleac M, Banica L, Casangiu C, Cotic M, Florea D, Sandulescu O, Milu P, Streinu-Cercel A, Vlaicu O, Paraskevis D, et al. Molecular Epidemiology Analysis of SARS-CoV-2 Strains Circulating in Romania during the First Months of the Pandemic. Life (Basel)Life (Basel)Life (Basel). 2020;10.Abstract
BACKGROUND: The spread of SARS-CoV-2 generated an unprecedented global public health crisis. Soon after Asia, Europe was seriously affected. Many countries, including Romania, adopted lockdown measures to limit the outbreak. AIM: We performed a molecular epidemiology analysis of SARS-CoV-2 viral strains circulating in Romania during the first two months of the epidemic in order to detect mutation profiles and phylogenetic relatedness. METHODS: Respiratory samples were directly used for shotgun sequencing. RESULTS: All Romanian sequences belonged to lineage B, with a different subtype distribution between northern and southern regions (subtype B.1.5 and B.1.1). Phylogenetic analysis suggested that the Romanian epidemic started with multiple introduction events from other European countries followed by local transmission. Phylogenetic links between northern Romania and Spain, Austria, Scotland and Russia were observed, as well as between southern Romania and Switzerland, Italy, France and Turkey. One viral strain presented a previously unreported mutation in the Nsp2 gene, namely K489E. Epidemiologically-defined clusters displayed specific mutations, suggesting molecular signatures for strains coming from areas that were isolated during the lockdown. CONCLUSIONS: Romanian epidemic was initiated by multiple introductions from European countries followed by local transmissions. Different subtype distribution between northern and southern Romania was observed after two months of the pandemic.
Thanasas I, Lavranos G, Gkogkou P, Paraskevis D. Understanding of Young Adolescents About HPV Infection: How Health Education Can Improve Vaccination Rate. J Cancer EducJ Cancer EducJ Cancer Educ. 2020;35:850-859.Abstract
The purpose of this systematic review was to identify adolescents' awareness on the human papillomavirus (HPV), the HPV vaccine, and the willingness to undergo the vaccination. A systematic review of studies concerning the adolescent's knowledge and education on the admission of the HPV vaccine was carried out, through the Medline/PubMed and the Google Scholar databases, covering information on adolescent attitudes towards HPV vaccination, as well as their perceptions regarding the vaccination and the need for more training, towards the public information about the HPV and the HPV vaccine. This study concludes that adolescents are poorly informed about the HPV and the preventive vaccination issues, underestimating the likelihood of the infection by the virus. The way to improve their knowledge about the HPV and the implications of the HPV infection is to provide information through the framework of compulsory schooling, primary health care, and the development of informative interactive interventions. The awareness for the need of training about the HPV and its implications should be broadened to address the major barrier to vaccination, which is regarded to be the lack of adequate information. The knowledge and the perceptible susceptibility to the HPV infection and HPV-related diseases among adolescents demonstrate the need for a well-designed training program to bridge the gap of information about the HPV virus and to accept the HPV vaccine.
Tsitsilonis OE, Paraskevis D, Lianidou E, Pierros V, Akalestos A, Kastritis E, Moutsatsou P, Scorilas A, Sphicopoulos T, Terpos E, et al. Seroprevalence of Antibodies against SARS-CoV-2 among the Personnel and Students of the National and Kapodistrian University of Athens, Greece: A Preliminary Report. Life (Basel)Life (Basel)Life (Basel). 2020;10.Abstract
Due to early implementation of public health measures, Greece had low number of SARS-CoV-2 infections and COVID-19 severe incidents in hospitalized patients. The National and Kapodistrian University of Athens (ΝΚUA), especially its health-care/medical personnel, has been actively involved in the first line of state responses to COVID-19. To estimate the prevalence of antibodies (Igs) against SARS-CoV-2 among NKUA members, we designed a five consecutive monthly serosurvey among randomly selected NKUA consenting volunteers. Here, we present the results from the first 2500 plasma samples collected during June-July 2020. Twenty-five donors were tested positive for anti-SARS-CoV-2 Igs; thus, the overall seroprevalence was 1.00%. The weighted overall seroprevalence was 0.93% (95% CI: 0.27, 2.09) and varied between males [1.05% (95% CI: 0.18, 2.92)] and females [0.84% (95% CI: 0.13, 2.49)], age-groups and different categories (higher in participants from the School of Health Sciences and in scientific affiliates/faculty members/laboratory assistants), but no statistical differences were detected. Although focused on the specific population of NKUA members, our study shows that the prevalence of anti-SARS-CoV-2 Igs for the period June-July 2020 remained low and provides knowledge of public health importance for the NKUA members. Given that approximately one in three infections was asymptomatic, continuous monitoring of the progression of the pandemic by assessing Ig seroprevalence is needed.
Morel B, Barbera P, Czech L, Bettisworth B, Hübner L, Lutteropp S, Serdari D, Kostaki EG, Mamais I, Kozlov AM, et al. Phylogenetic analysis of SARS-CoV-2 data is difficult. Mol Biol EvolMol Biol EvolMol Biol Evol. 2020.Abstract
Numerous studies covering some aspects of SARS-CoV-2 data analyses are being published on a daily basis, including a regularly updated phylogeny on nextstrain.org. Here, we review the difficulties of inferring reliable phylogenies by example of a data snapshot comprising a quality-filtered subset of 8, 736 out of all 16, 453 virus sequences available on May 5, 2020 from gisaid.org. We find that it is difficult to infer a reliable phylogeny on these data due to the large number of sequences in conjunction with the low number of mutations. We further find that rooting the inferred phylogeny with some degree of confidence either via the bat and pangolin outgroups or by applying novel computational methods on the ingroup phylogeny does not appear to be credible. Finally, an automatic classification of the current sequences into sub-classes using the mPTP tool for molecular species delimitation is also, as might be expected, not possible, as the sequences are too closely related. We conclude that, although the application of phylogenetic methods to disentangle the evolution and spread of COVID-19 provides some insight, results of phylogenetic analyses, in particular those conducted under the default settings of current phylogenetic inference tools, as well as downstream analyses on the inferred phylogenies, should be considered and interpreted with extreme caution.
Paraskevis D, Kostaki EG. An evolving genetic tapestry of HIV-1 recombinants. Lancet HIVLancet HIVLancet HIV. 2020;7:e733-e734.
Paraskevis D, Kostaki EG, Magiorkinis G, Panayiotakopoulos G, Sourvinos G, Tsiodras S. Full-genome evolutionary analysis of the novel corona virus (2019-nCoV) rejects the hypothesis of emergence as a result of a recent recombination event. Infect Genet EvolInfect Genet EvolInfect Genet Evol. 2020;79:104212.Abstract
BACKGROUND: A novel coronavirus (2019-nCoV) associated with human to human transmission and severe human infection has been recently reported from the city of Wuhan in China. Our objectives were to characterize the genetic relationships of the 2019-nCoV and to search for putative recombination within the subgenus of sarbecovirus. METHODS: Putative recombination was investigated by RDP4 and Simplot v3.5.1 and discordant phylogenetic clustering in individual genomic fragments was confirmed by phylogenetic analysis using maximum likelihood and Bayesian methods. RESULTS: Our analysis suggests that the 2019-nCoV although closely related to BatCoV RaTG13 sequence throughout the genome (sequence similarity 96.3%), shows discordant clustering with the Bat_SARS-like coronavirus sequences. Specifically, in the 5'-part spanning the first 11,498 nucleotides and the last 3'-part spanning 24,341-30,696 positions, 2019-nCoV and RaTG13 formed a single cluster with Bat_SARS-like coronavirus sequences, whereas in the middle region spanning the 3'-end of ORF1a, the ORF1b and almost half of the spike regions, 2019-nCoV and RaTG13 grouped in a separate distant lineage within the sarbecovirus branch. CONCLUSIONS: The levels of genetic similarity between the 2019-nCoV and RaTG13 suggest that the latter does not provide the exact variant that caused the outbreak in humans, but the hypothesis that 2019-nCoV has originated from bats is very likely. We show evidence that the novel coronavirus (2019-nCov) is not-mosaic consisting in almost half of its genome of a distinct lineage within the betacoronavirus. These genomic features and their potential association with virus characteristics and virulence in humans need further attention.
Pogka V, Horefti E, Evangelidou M, Kostaki EG, Paraskevis D, Flountzi A, Georgakopoulou T, Magaziotou I, Mentis A, Karamitros T. Spatiotemporal Distribution and Genetic Characterization of Measles Strains Circulating in Greece during the 2017-2018 Outbreak. VirusesVirusesViruses. 2020;12.Abstract
Between May 2017 and November 2018, Greece has experienced a severe measles outbreak with a total of 3258 cases reported, after reaching its goal of eliminating measles since 2014-2015. In this study, we aimed to investigate the origin and the dispersal patterns of the measles strains that circulated in Greece during this outbreak and to identify possible transmission patterns of measles virus (MeV) in the country. Of the 832 measles suspect cases referred to the National Measles and Rubella Reference Laboratory for MeV RNA detection, 131 randomly selected positive samples, representative of the temporal and spatial distribution of the laboratory-confirmed measles cases in Greece, were processed for genotypic identification by an RT-PCR amplification of a 598 bp fragment containing the 450 bp hypervariable region of the measles virus N gene. Phylogenetic analysis was carried out by the approximate maximum likelihood method (ML) under the generalized time-reversible (GTR + cat) model. All samples analyzed were found to belong to genotype B3. Comparative analysis with other European and reference measles strains revealed three separate major clusters and other multiple viruses circulating simultaneously in Greece. They were all isolated from three main community groups, Greek-Roma children, non-minority Greek nationals and immigrants/refugees, a finding that is in accordance with what was also observed in the last two measles outbreaks in 2005-2006 and 2010-2011. Notably, for one of the three clusters, no similarity was detected with previously reported prototype strains. Our results indicate the need for a more intensive vaccination program against measles amongst minority populations and in refugee hot-spots as well as the importance of molecular surveillance as a tool for monitoring measles outbreaks.
Kostaki EG, Gova M, Adamis G, Xylomenos G, Chini M, Mangafas N, Lazanas M, Metallidis S, Tsachouridou O, Papastamopoulos V, et al. A Nationwide Study about the Dispersal Patterns of the Predominant HIV-1 Subtypes A1 and B in Greece: Inference of the Molecular Transmission Clusters. VirusesVirusesViruses. 2020;12.Abstract
Our aim was to investigate the dispersal patterns and parameters associated with local molecular transmission clusters (MTCs) of subtypes A1 and B in Greece (predominant HIV-1 subtypes). The analysis focused on 1751 (28.4%) and 2575 (41.8%) sequences of subtype A1 and B, respectively. Identification of MTCs was based on phylogenetic analysis. The analyses identified 38 MTCs including 2-1518 subtype A1 sequences and 168 MTCs in the range of 2-218 subtype B sequences. The proportion of sequences within MTCs was 93.8% (1642/1751) and 77.0% (1982/2575) for subtype A1 and B, respectively. Transmissions within MTCs for subtype A1 were associated with risk group (Men having Sex with Men vs. heterosexuals, OR = 5.34, p < 0.001) and Greek origin (Greek vs. non-Greek origin, OR = 6.05, p < 0.001) and for subtype B, they were associated with Greek origin (Greek vs. non-Greek origin, OR = 1.57, p = 0.019), younger age (OR = 0.96, p < 0.001), and more recent sampling (time period: 2011-2015 vs. 1999-2005, OR = 3.83, p < 0.001). Our findings about the patterns of across and within country dispersal as well as the parameters associated with transmission within MTCs provide a framework for the application of the study of molecular clusters for HIV prevention.
Kostaki EG, Hodges-Mameletzis I, Magiorkinis G, Adamis G, Xylomenos G, Nikolopoulos G, Lazanas M, Chini M, Mangafas N, Skoutelis A, et al. Earlier treatment initiation is associated with a decreased number of HIV-1 subtype A1 transmissions in Greece. Sex Transm InfectSex Transm InfectSex Transm Infect. 2020.Abstract
OBJECTIVES: Subtypes A1 and B are the most prevalent HIV-1 clades in Greece. Subtype A1 epidemic is highly monophyletic and corresponds to transmissions that occurred locally. Our aim in this molecular epidemiology analysis was to investigate the role of early treatment in preventing new HIV-1 transmissions. METHODS: Our analysis focused on 791 subtype A1 sequences from treatment-naïve individuals in Greece. Estimation of infection dates was performed by molecular clock calculations using Bayesian methods. We estimated the time interval between (1) the infection and sampling dates (linkage to care window), (2) the sampling dates and antiretroviral therapy (ART) initiation (treatment window), and (3) the infection dates and ART initiation (transmissibility window) for the study population. We also inferred the putative source of HIV infections between individuals of different groups divided according to the length of treatment, linkage to care or transmissibility window. RESULTS: A significant decline was detected for the treatment window during 2014-2015 versus the 2 previous years (p=0.0273), while the linkage to care interval remained unchanged during the study period. Inference of the putative source of HIV infections suggested that individuals with a recent diagnosis or narrow transmissibility window (time period between HIV infection and ART initiation) were not sources of HIV infections to other groups. Contrarily, a significant number of HIV infections originated from individuals with longer transmissibility window interval. CONCLUSIONS: Our findings showed that the treatment window is decreasing over time, presumably due to the updated treatment guidelines. Our study also demonstrates that people treated earlier after infection do not transmit at high rates, thus documenting the benefits of early ART initiation in preventing ongoing HIV-1 transmission.
Alygizakis N, Markou AN, Rousis NI, Galani A, Avgeris M, Adamopoulos PG, Scorilas A, Lianidou ES, Paraskevis D, Tsiodras S, et al. Analytical methodologies for the detection of SARS-CoV-2 in wastewater: Protocols and future perspectives. Trends Analyt ChemTrends Analyt ChemTrends Analyt Chem. 2020:116125.Abstract
In March 2020 the World Health Organization announced a pandemic outbreak. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative pathogen for the coronavirus disease-19 (COVID-19) pandemic. The authorities worldwide use clinical science to identify infected people, but this approach is not able to track all symptomatic and asymptomatic cases due to limited sampling capacity of the testing laboratories. This drawback is eliminated by the Wastewater-Based Epidemiology (WBE) approach. In this review, we summarized the peer-reviewed published literature (available as of 28(th) September 2020), in the field of WBE. The commonly used steps (sampling, storage, concentration, isolation, detection) of the analytical protocols were identified. The potential limitations of each stage of the protocols and good practices were discussed. Finally, new methods for the efficient detection of SARS-CoV-2 were proposed.
Ingasia LAO, Kostaki EG, Paraskevis D, Kramvis A. Global and regional dispersal patterns of hepatitis B virus genotype E from and in Africa: A full-genome molecular analysis. PLoS OnePLoS OnePLoS One. 2020;15:e0240375.Abstract
Description of the spatial characteristics of viral dispersal is important in understanding the history of infections. Nine hepatitis B virus (HBV) genotypes (A-I), and a putative 10th genotype (J), with distinct geographical distribution, are recognized. In sub-Saharan Africa (sub)-genotypes A1, D3 and E circulate, with E predominating in western Africa (WA), where HBV is hyperendemic. The low genetic diversity of genotype E (HBV/E) suggests its recent emergence. Our aim was to study the dispersal of HBV/E using full-length, non-redundant and non-recombinant sequences available in public databases. HBV/E was confirmed, and the phylogeny reconstruction performed using maximum likelihood (ML) with bootstrapping. Phylogeographic analysis was conducted by reconstruction of ancestral states using the criterion of parsimony on the estimated ML phylogeny. 46.5% of HBV/E sequences were found within monophyletic clusters. Country-wise analysis revealed the existence of 50 regional clusters. Sequences from WA were located close to the root of the tree, indicating this region as the most probable origin of the HBV/E epidemic and expanded to other geographical regions, within and outside of Africa. A localized dispersal was observed with sequences from Nigeria and Guinea as compared to other WA countries. Based on the sequences available in the databases, the phylogenetic results suggest that European strains originated primarily from WA whereas a majority of American strains originated in Western Central Africa. The differences in regional dispersal patterns of HBV/E suggest limited cross-border transmissions because of restricted population movements.
Kefala AM, Fortescue R, Alimani GS, Kanavidis P, McDonnell MJ, Magiorkinis E, Megremis S, Paraskevis D, Voyiatzaki C, Mathioudakis GA, et al. Prevalence and clinical implications of respiratory viruses in stable chronic obstructive pulmonary disease (COPD) and exacerbations: a systematic review and meta-analysis protocol. BMJ OpenBMJ OpenBMJ Open. 2020;10:e035640.Abstract
INTRODUCTION: Both stable chronic obstructive pulmonary disease (COPD) and acute exacerbations represent leading causes of death, disability and healthcare expenditure. They are complex, heterogeneous and their mechanisms are poorly understood. The role of respiratory viruses has been studied extensively but is still not adequately addressed clinically. Through a rigorous evidence update, we aim to define the prevalence and clinical burden of the different respiratory viruses in stable COPD and exacerbations, and to investigate whether viral load of usual respiratory viruses could be used for diagnosis of exacerbations triggered by viruses, which are currently not diagnosed or treated aetiologically. METHODS AND ANALYSIS: Based on a prospectively registered protocol, we will systematically review the literature using standard methods recommended by the Cochrane Collaboration and the Grading of Recommendations Assessment, Development and Evaluation working group. We will search Medline/PubMed, Excerpta Medica dataBASE (EMBASE), the Cochrane Library, the WHO's Clinical Trials Registry and the proceedings of relevant international conferences on 2 March 2020. We will evaluate: (A) the prevalence of respiratory viruses in stable COPD and exacerbations, (B) differences in the viral loads of respiratory viruses in stable COPD vs exacerbations, to explore whether the viral load of prevalent respiratory viruses could be used as a diagnostic biomarker for exacerbations triggered by viruses and (C) the association between the presence of respiratory viruses and clinical outcomes in stable COPD and in exacerbations. ETHICS AND DISSEMINATION: Ethics approval is not required since no primary data will be collected. Our findings will be presented in national and international scientific conferences and will be published in peer reviewed journals. Respiratory viruses currently represent a lost opportunity to improve the outcomes of both stable COPD and exacerbations. Our work aspires to 'demystify' the prevalence and clinical burden of viruses in stable COPD and exacerbations and to promote clinical and translational research. PROSPERO REGISTRATION NUMBER: CRD42019147658.
Kirichenko A, Lapovok I, Baryshev P, van de Vijver DAMC, van Kampen JJA, Boucher CAB, Paraskevis D, Kireev D. Genetic Features of HIV-1 Integrase Sub-Subtype A6 Predominant in Russia and Predicted Susceptibility to INSTIs. VirusesVirusesViruses. 2020;12.Abstract
The increasing use of the integrase strand transfer inhibitor (INSTI) class for the treatment of HIV-infection has pointed to the importance of analyzing the features of HIV-1 subtypes for an improved understanding of viral genetic variability in the occurrence of drug resistance (DR). In this study, we have described the prevalence of INSTI DR in a Russian cohort and the genetic features of HIV-1 integrase sub-subtype A6. We included 408 HIV infected patients who were not exposed to INSTI. Drug resistance mutations (DRMs) were detected among 1.3% of ART-naïve patients and among 2.7% of INSTI-naïve patients. The prevalence of 12 polymorphic mutations was significantly different between sub-subtypes A6 and A1. Analysis of the genetic barriers determined two positions in which subtype A (A1 and A6) showed a higher genetic barrier (G140C and V151I) compared with subtype B, and one position in which subtypes A1 and B displayed a higher genetic barrier (L74M and L74I) than sub-subtype A6. Additionally, we confirmed that the L74I mutation was selected at the early stage of the epidemic and subsequently spread as a founder effect in Russia. Our data have added to the overall understanding of the genetic features of sub-subtype A6 in the context of drug resistance.