Study On The Propagation Of Human Influenza A Virus From Global Prospect

Influenza has ravaged human life for a long time. Especially since the 20 th century, the variability of influenza virus caused several serious pandemic of humanized influenza A. Influenza A virus has strong variability, resulting in a powerful ability to spread of flu epidemic. The increasing development of transport has also greatly accelerated the propagation speed of flu epidemic. The two points mentioned above has made the prevention and control of influenza virus become a extremely difficult problem all over the world.In this paper, we take the global influenza surveillance data as the research object. And the bioinformatics thechnics combined with location and time of the epidemics are used to explore the propagation characteristics of human Influenza A virus. The obtained results are expected to accurately analyze the recent propagation characteristics of human influenza A timely and accurately from a global perspective, which can provide theoretical foundation for prevention of influenza epidemics.The thesis presents two kinds of similarity classification methods of viral sequences. On the basis of classification, spread network of influenza virus is established. Through analysis of the network parameters, influenza virus propagation characteristics are excavated, which is as a theoretical basis and foundation for the prevention and treatment of influenza epidemics. The main work of this paper is as follows.(1)Two feature extraction methods of protein sequences are presented. The paper proposes human Influenza A virus HA protein gene sequence similarity calculation method based on the two feature extraction methods. The validity of the similarity calculation method has been verified by the similarity analysis in the classical ND9 protein sequence and in 24 influenza A virus protein sequences.(2)Method of establishing a global context human Influenza A virus transmission network is presented. Firstly, the sequences of feature vectors were dimensionality reduction clustering by PCA, isolating into several variation subgroup. Then we take the citys as nodes in the network and take generational spread as a spreading model to establish transmission network of new virus samples. Also, several parameters as characteristic indicators of influenza virus transmission network are proposed, such as node degree, propagation distance, propagation time, propagation speed are several important characteristics of indicators about the propagation breadth and propagation speed in exploring the propagation characteristics of influenza A virus.(3)The transmission networks of Human influenza A H1N1 and H3N2 from 1975 to 2015 are constructed. Network parameters are as characteristic indexes to indicate the propagation characteristics of Human Influenza A H1N1 and H3N2 influenza virus in global context form 1975 to 2015.