Análisis de factores epidemiológicos que afectan a la dispersión de virus

Abstract

The current covid-19 epidemic has highlighted the huge impact that virus-borne diseases can have not only on the health of individuals but also on the economy and society of countries. To end the current pandemic and prevent future ones, it is necessary to understand the factors that have enabled SARS-CoV-to reach an unprecedented level of global distribution and prevalence. At the root of this epidemiological "success" is the rapid spread of the virus from its source in China and its ability to evolve, which has allowed the virus to optimise its infectivity in humans and rapidly generate new variants in humans. The purpose of this project is to identify the environmental factors that may favour the spread of SARS-CoV 2 globally. The project is divided into 3 secondary objectives: 1) Collection of SARS-CoV 2 S protein gene sequences from 80 countries available in public databases and construction of phylogenetic trees with these sequences, 2) collection of information on different epidemiological, demographic and economic variables that may have an effect on the spread of the virus, 3) reconstruction of SARS-CoV 2 spatial dispersal patterns using phylogenetic approaches and determination of the factors that favour the process of virus dispersal between countries. The first step was to collect the 1865 SARS-CoV-2 sequences. Once the sequences were obtained, a maximum likelihood tree was performed with them. The results of the tree showed that the virus has a temporal structure, and its closest common ancestor belongs to December 2019, which is consistent with the real values. The spatial dispersion patterns of SARS-CoV-2 were then reconstructed using Bayesian approaches based on Markov Chain Monte Carlo (MCMC) using the S gene sequences. In addition, General Linear Models (GLM) were used to analyse the effect of environmental variables on virus dispersal patterns and coupled to phylogenetic reconstruction. The variables used in the general linear model were collected from different databases, using environmental, social and economic variables. Dispersion analyses determined that the origin of SARS-CoV-2 was China, and that the first country to which it spread was England, constituting the first major source of infection in the world apart from China. Analysis of the GLM results indicated that the only variable that may be affecting the spread of SARS-CoV 2 is mean age, which is negatively associated with spread. In conclusion, the results provided by this study indicate that SARS-CoV-2 entered Europe through England, and that the variable related to dispersion within all selected variables was mean age.