RESUMO
Since the start of the coronavirus disease 2019 (COVID-19) pandemic, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly widespread worldwide becoming one of the major global public health issues of the last centuries. Currently, COVID-19 vaccine rollouts are finally upon us carrying the hope of herd immunity once a sufficient proportion of the population has been vaccinated or infected, as a new horizon. However, the emergence of SARS-CoV-2 variants brought concerns since, as the virus is exposed to environmental selection pressures, it can mutate and evolve, generating variants that may possess enhanced virulence. Codon usage analysis is a strategy to elucidate the evolutionary pressure of the viral genome suffered by different hosts, as possible cause of the emergence of new variants. Therefore, to get a better picture of the SARS-CoV-2 codon bias, we first identified the relative codon usage rate of all Betacoronaviruses lineages. Subsequently, we correlated putative cognate transfer ribonucleic acid (tRNAs) to reveal how those viruses adapt to hosts in relation to their preferred codon usage. Our analysis revealed seven preferred codons located in three different open reading frame which appear preferentially used by SARS-CoV-2. In addition, the tRNA adaptation analysis indicates a wide strategy of competition between the virus and mammalian as principal hosts highlighting the importance to reinforce the genomic monitoring to prompt identify any potential adaptation of the virus into new potential hosts which appear to be crucial to prevent and mitigate the pandemic.
Assuntos
Betacoronavirus/genética , Uso do Códon , Infecções por Coronavirus/virologia , Genoma Viral , Mamíferos , SARS-CoV-2/genética , Animais , COVID-19 , Vacinas contra COVID-19 , Códon , Interações Hospedeiro-Patógeno , Humanos , Mutação , Fases de Leitura Aberta , Filogenia , RNA de TransferênciaRESUMO
We investigated SARS-CoV-2 transmission dynamics in Italy, one of the countries hit hardest by the pandemic, using phylodynamic analysis of viral genetic and epidemiological data. We observed the co-circulation of multiple SARS-CoV-2 lineages over time, which were linked to multiple importations and characterized by large transmission clusters concomitant with a high number of infections. Subsequent implementation of a three-phase nationwide lockdown strategy greatly reduced infection numbers and hospitalizations. Yet we present evidence of sustained viral spread among sporadic clusters acting as "hidden reservoirs" during summer 2020. Mathematical modelling shows that increased mobility among residents eventually catalyzed the coalescence of such clusters, thus driving up the number of infections and initiating a new epidemic wave. Our results suggest that the efficacy of public health interventions is, ultimately, limited by the size and structure of epidemic reservoirs, which may warrant prioritization during vaccine deployment.
Assuntos
COVID-19/transmissão , Controle de Doenças Transmissíveis/métodos , Genoma Viral/genética , Mutação , Saúde Pública/métodos , SARS-CoV-2/genética , COVID-19/epidemiologia , COVID-19/virologia , Geografia , Humanos , Itália/epidemiologia , Pandemias , Filogenia , Saúde Pública/tendências , SARS-CoV-2/classificação , SARS-CoV-2/fisiologiaRESUMO
The emergence of the novel betacoronavirus, recently renamed as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has raised serious concerns due to the virus's rapid dissemination worldwide. Nevertheless, there is limited information about the genomic epidemiology of SARS-CoV-2 circulating in Italy from surveillance studies. The shortage of complete genomic sequences available impairs our understanding of the SARS-CoV-2 introduction and establishment in the country. To better understand its dynamics in Italy, we analyzed complete genomes of SARS-CoV-2 isolates, obtained directly from clinical samples. Our phylogenetic reconstructions suggest possible multiple introduction of SARS-CoV-2. Continued genomic surveillance strategies are needed to improve monitoring and understanding of the current SARS-CoV-2 epidemics, which might help to attenuate public health impact of infectious diseases.
Assuntos
COVID-19/epidemiologia , COVID-19/virologia , SARS-CoV-2 , Biologia Computacional , Genoma Viral , Genômica/métodos , Genótipo , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Itália/epidemiologia , Pandemias , Filogenia , Vigilância em Saúde Pública , SARS-CoV-2/classificação , SARS-CoV-2/genéticaRESUMO
A novel Coronavirus, 2019-nCoV, has been identified as the causal pathogen of an ongoing epidemic, with the first cases reported in Wuhan, China, last December 2019, and has since spread to other countries worldwide, included Europe and very recently Italy. In this short report, phylogenetic reconstruction was used to better understand the transmission dynamics of the virus from its first introduction in China focusing on the more recent evidence of infection in a couple of Chinese tourists arrived in Italy on 23rd January 2020 and labeled as Coronavirus Italian cases. A maximum clade credibility tree has been built using a dataset of 54 genome sequences of 2019-nCoV plus two closely related bat strains (SARS-like CoV) available in GenBank. Bayesian time-scaled phylogenetic analysis was implemented in BEAST 1.10.4. The Bayesian phylogenetic reconstruction showed that 2019-2020 nCoV firstly introduced in Wuhan on 25 November 2019, started epidemic transmission reaching many countries worldwide, including Europe and Italy where the two strains isolated dated back 19 January 2020, the same that the Chinese tourists arrived in Italy. Strains isolated outside China were intermixed with strains isolated in China as evidence of likely imported cases in Rome, Italy, and Europe, as well. In conclusion, this report suggests that further spread of 2019-nCoV epidemic was supported by human mobility and that quarantine of suspected or diagnosed cases is useful to prevent further transmission. Viral genome phylogenetic analysis represents a useful tool for the evaluation of transmission dynamics and preventive action.
Assuntos
Betacoronavirus/genética , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/transmissão , Genoma Viral , Pneumonia Viral/epidemiologia , Pneumonia Viral/transmissão , Animais , Betacoronavirus/isolamento & purificação , COVID-19 , Quirópteros/virologia , Humanos , Bloqueio Interatrial , Itália/epidemiologia , Modelos Genéticos , Taxa de Mutação , Pandemias , Filogenia , SARS-CoV-2RESUMO
Madariaga Virus (MADV) is an emergent Alphavirus of the eastern equine encephalitis virus (EEEV) strain complex causing epizootic epidemics. In this study the genetic diversity and the transmission dynamics of Madariaga virus has been investigated by Bayesian phylogenetics and phylodynamic analysis. A database of 32 sequences of MADV group structural polyprotein were downloaded from GenBank, aligned manually edited by Bioedit Software. ModelTest v. 3.7 was used to select the simplest evolutionary model that adequately fitted the sequence data. Neighbor-joining tree was generated using MEGA7. The phylogenetic signal of the dataset was tested by the likelihood mapping analysis. The Bayesian phylogenetic tree was built using BEAST. Selective pressure analysis revealed one positive selection site. The phylogenetic trees showed two main clusters. In particular, Lineage II showed an epizootic infection in monkeys and Lineage III, including 2 main clusters (IIIa and IIIB), revealing an epizootic infection in humans in Haiti and an epizootic infection in humans in Venezuela during the 2016, respectively. The Bayesian maximum clade credibility tree and the time of the most common recent ancestor estimates, showed that the root of the tree dated back to the year 346 with the probable origin in Brazil. Gene flow analysis revealed viral exchanges between different neighbor countries of South America. In conclusion, Bayesian phylogenetic and phylodynamic represent useful tools to follow the transmission dynamic of emergent pathogens to prevent new epidemics spreading worldwide.
Assuntos
Vírus da Encefalite Equina do Leste/genética , Vírus da Encefalite Equina do Leste/patogenicidade , Encefalomielite Equina/epidemiologia , Encefalomielite Equina/transmissão , Encefalomielite Equina/virologia , Filogenia , Infecções por Alphavirus , Animais , Sequência de Bases , Teorema de Bayes , Brasil , Vírus da Encefalite Equina do Leste/classificação , Epidemias , Evolução Molecular , Fluxo Gênico , Variação Genética , Haiti , Haplorrinos , Humanos , RNA Viral/genética , Alinhamento de Sequência , América do Sul , VenezuelaRESUMO
Shigella infections account for a considerable burden of acute diarrheal diseases worldwide and remain a major cause of childhood mortality in developing countries. Although, all four species of Shigella (S. dysenteriae, S. flexneri, S. boydii, and S. sonnei) cause bacillary dysentery, historically only S. dysenteriae type 1 has been recognized as carrying the genes for Shiga toxin (stx). Recent epidemiological data, however, have suggested that the emergence of stx carrying S. flexneri strains may have originated from bacteriophage-mediated inter-species horizontal gene transfer in one specific geographical area, Hispaniola. To test this hypothesis, we analyzed whole genome sequences of stx-encoding phages carried by S. flexneri strains isolated in Haiti and S. flexneri S. boydii and S. dysenteriae strains isolated from international travelers who likely acquired the infection in Haiti or the Dominican Republic. Phylogenetic analysis showed that phage sequences encoded in the Shigella strains from Hispaniola were bacteriophage φPOC-J13 and they were all closely related to a phage isolated from a USA isolate, E. coli 2009C-3133 serotype O119:H4. In addition, despite the low genetic heterogeneity of phages from different Shigella spp. circulating in the Caribbean island between 2001 and 2014, two distinct clusters emerged in Haiti and the Dominican Republic. Each cluster possibly originated from phages isolated from S. flexneri 2a, and within each cluster several instances of horizontal phage transfer from S. flexneri 2a to other species were detected. The implications of the emergence of stx-producing non-S. dysenteriae type 1 Shigella species, such as S. flexneri, spans not only the basic science behind horizontal phage spread, but also extends to medical treatment of patients infected with this pathogen.