ARTICLE | doi:10.20944/preprints202012.0310.v1
Subject: Life Sciences, Biochemistry Keywords: Variola major; phylogeographical analysis; long-term calibrations; short- term calibrations
Online: 14 December 2020 (09:21:34 CET)
In order to reconstruct the origin and pathways of variola virus (VARV) dispersion, we analyzed 47 VARV isolates available in public databases and their SNPs. The mean substitution rate of the whole genomes was 9.41x10-6 (95%HPD:8.5-11.3x10-6) substitutions/site/year. The time of the tree root was estimated to be a mean 68 years (95%HPD:60.5–75.9). The phylogeographical analysis showed that the Far East and India were the most probable locations of the tree root and of the inner nodes, respectively, whereas for the outer nodes it corresponded to the sampling locations. The Bayesian Skyline plot showed that the effective number of infections started to grow exponentially in 1915-1920, peaked in the 1940s, and then decreased to zero. Our results suggests that the VARV major strains circulating between 1940s-1970s probably shared a common ancestor originated in the Far East; subsequently moved to India, which became the center of its dispersion to eastern and southern Africa, and then to central Africa and the Middle East, probably following the movements of people between south-eastern Asia and the other places with a common colonial history. These findings may help to explain the controversial reconstructions of the history of VARV obtained using long- and short- term calibrations.
ARTICLE | doi:10.20944/preprints202101.0198.v1
Subject: Life Sciences, Virology Keywords: epidemiological history of HCV-2; HCV-2 subtypes; evolutionary demography of HCV-2; phylodynamics of HCV-2 in Italy and Albania; HCV-2 Re estimation
Online: 11 January 2021 (13:10:30 CET)
Newly characterising 245 Italian and Albanian HCV-2 NS5B sequences collected between 2001 and 2016 was used to reconstruct the origin and dispersion pathways of HCV-2c. The tree of a subset of these sequences aligned with 247 publicly available sequences was reconstructed in spatio-temporal scale using the Bayesian approach, and the effective replication number (Re) was estimated using the birth-death model. Our findings show that HCV-2c was the most prevalent subtype in Italy and Albania, and that GT2 originated in Guinea Bissau in the XVI century and spread to Europe in the XX century. The HCV-2c subtype had two internal nodes respectively dating back to the 1930s and 1950s having as most probable locations Ghana and Italy, respectively. Phylodynamic analysis revealed an exponential increase in the effective number of infections and Re in both Italy between the 1950s and 1980s, and Albania between the 1990s and the early 2000s. It seems very likely that HCV-2c reached Italy from Africa at the time of the second Italian colonisation (1936-1941), but did not reach Albania until the period of dramatic migration to Italy in the 1990s.
ARTICLE | doi:10.20944/preprints202007.0144.v1
Subject: Life Sciences, Virology Keywords: phylodynamic analyses; SARS-CoV2 circulation in Italy; molecular tracing; Whole Genome Sequencing
Online: 8 July 2020 (11:00:19 CEST)
The aim of this study is the characterization and genomic tracing by phylogenetic analyses of 59 new SARS-CoV-2 Italian isolates obtained from patients attending clinical centres in North and Central Italy until the end of April 2020. All but one of the newly characterized genomes belonged to the lineage B.1, the most frequently identified in European countries, including Italy. Only a single sequence was found to belong to lineage B. A mean of 6 nucleotide substitutions per viral genome was observed, without significant differences between synonymous and non-synonymous mutations, indicating genetic drift as a major source for virus evolution. tMRCA estimation confirmed the probable origin of the epidemic between the end of January and the beginning of February with a rapid increase in the number of infections between the end of February and mid-March. Since early February, an effective reproduction number (Re) greater than 1 was estimated, which then increased reaching the peak of 2.3 in early March, confirming the circulation of the virus before the first COVID-19 cases were documented. Continuous use of state-of-the-art methods for molecular surveillance is warranted to trace virus circulation and evolution and inform effective prevention and containment of future SARS-CoV-2 outbreaks.
BRIEF REPORT | doi:10.20944/preprints202105.0526.v1
Subject: Life Sciences, Biochemistry Keywords: SARS-CoV-2 virus; complete genome sequencing; COVID-19 RT-PCR testing; Spike protein; vi-ral variants
Online: 21 May 2021 (15:12:17 CEST)
A growing number of emerging SARS-CoV-2 variants is being identified worldwide, potentially impacting the effectiveness of current vaccines. We report the data obtained in several Italian regions involved in the SARS-CoV-2 variant monitoring from the beginning of the epidemic and spanning the period from October 2020 to March 2021.
ARTICLE | doi:10.20944/preprints202107.0654.v1
Online: 29 July 2021 (12:23:23 CEST)
The aim of this study was the reconstruction of SARS-CoV-2 evolutionary dynamics in time and space in Italy and Europe between February and June 2020. The cluster analysis showed that pure Italian clusters were observed mainly after the lockdown and distancing measures were adopted. Lineage B and B.1 spread between late January and early February 2020, from China to Veneto and Lombardy, respectively. Lineage B.1.1 most probably evolved within Italy and spread from central to south Italian regions, and to European countries. The lineage B.1.1.1 entered Italy only in the second half of March and remained localized in Piedmont until June 2020. In conclusion, the reconstructed ancestral scenario suggests a central role of China and Italy in the widespread diffusion of the D614G variant in Europe in the early phase of the pandemic and more dispersed exchanges involving several European countries from the second half of March 2020.
ARTICLE | doi:10.20944/preprints202209.0241.v1
Online: 16 September 2022 (08:07:10 CEST)
SARS-CoV-2 is constantly evolving leading to new variants. We analysed data from 4,400 SARS-CoV-2-positive samples in order to continue variant surveillance in Italy to evaluate their epidemiological and relative impact on public health in the period April-December 2021. The main circulating strain (76.2%) was Delta followed by Alpha (13.3%), Omicron (5.3%) and Gamma variants (2.9%). B.1.1 lineages, Eta, Beta, Iota, Mu and Kappa variants represented around 1% of cases. Overall, 48.2% of subjects were not vaccinated with a lower median age compared to vaccinated subjects (47 vs. 61 years). An increasing number of infections in vaccinated subjects was observed overtime, with the highest proportion in November (85.2%). Variants correlated with clinical status; the largest proportion of symptomatic patients (59.6%) was observed among Delta variant, while subjects harboring Gamma variant showed the highest proportion of asymptomatics (21.6%), albeit also of deaths (5.4%). The Omicron variant was only found in vac-cinated subjects, of which 47% were hospitalized. Diffusivity and pathogenicity associated with the different SARS-CoV-2 variants are likely to have relevant public health implications, both at national and international level. Our study pro-vides data on the rapid changes in the epidemiological landscape of SARS-CoV-2 variants in Italy.