A network approach to understanding pathogen population structure

Many biological processes are best understood as networks of interactions or relationships between constituent parts. In the context of pathogen evolution and dynamics, for example, it has long been recognized that the assumption of random mixing among hosts in many theoretical models is almost always violated in reality. Hosts mix locally and heterogeneously, with mixing patterns reflecting the mode of pathogen transmission. We explore how different assumptions about host contact network structure affect the structure and evolution of pathogen populations. Recently, the idea that networks may also represent relationships between the antigens of genetically diverse pathogen species better than traditional phylogenetic techniques has emerged. We discuss the structure and implications of an antigenic network of the malaria parasite, Plasmodium falciparum. Here, the relationship between different antigenic variants is envisaged as a network representing recombination events and can be related to observed serological relationships between parasite isolates. In addition, the role of antigenic networks in driving the dynamics of single-strain outbreaks of a very different pathogen, the influenza virus, is highlighted. © 2010 Springer-Verlag New York.