Murray State University
Epidemiology as Related to Phylogenetic Distances of the Influenza Virus
Institution
Murray State University
Faculty Advisor/ Mentor
Linda Gao
Abstract
The evolution of the influenza virus is characterized by continual changes to its surface structures due to antigenic drift and antigenic shift. In response, the host immune system must alter antibodies in response to the ever-changing virus allowing for the persistence of influenza in a host population. The spread of related strains to a susceptible population with regard to their phylogenetic distance from a parental strain during a season is examined, as well as the dynamics of the immune response within a single host. Very little work has been done to integrate phylogenetic analysis of evolution with the epidemiological spread of the influenza virus. In this study, an attempt is made to couple these two scales by using infection rates that are defined as functions of phylogenetic distances between strains. Competition between strains is focused on and strain prevalence for outbreaks during several seasons (2000-2004, inclusive) is examined at various levels: global, regional, and for New York City. Coexistence is found to only be possible between very similar strains, otherwise competitive exclusion or extinction of all strains occur. Stochastic simulations at the cellular level indicate that the immune system is most effective when the virus has little variability, so the rapid mutation of influenza is an effective strategy in evading the immune system. Similar simulations for the population level show that a strain's prevalence depends largely on the level of change in antigenic structure is produced by amino acid mutations.
Epidemiology as Related to Phylogenetic Distances of the Influenza Virus
The evolution of the influenza virus is characterized by continual changes to its surface structures due to antigenic drift and antigenic shift. In response, the host immune system must alter antibodies in response to the ever-changing virus allowing for the persistence of influenza in a host population. The spread of related strains to a susceptible population with regard to their phylogenetic distance from a parental strain during a season is examined, as well as the dynamics of the immune response within a single host. Very little work has been done to integrate phylogenetic analysis of evolution with the epidemiological spread of the influenza virus. In this study, an attempt is made to couple these two scales by using infection rates that are defined as functions of phylogenetic distances between strains. Competition between strains is focused on and strain prevalence for outbreaks during several seasons (2000-2004, inclusive) is examined at various levels: global, regional, and for New York City. Coexistence is found to only be possible between very similar strains, otherwise competitive exclusion or extinction of all strains occur. Stochastic simulations at the cellular level indicate that the immune system is most effective when the virus has little variability, so the rapid mutation of influenza is an effective strategy in evading the immune system. Similar simulations for the population level show that a strain's prevalence depends largely on the level of change in antigenic structure is produced by amino acid mutations.