title: Serotype cycles in cholera dynamics.
abstract: Interest in understanding strain diversity and its impact on disease dynamics has grown over the past decade. Theoretical disease models of several co-circulating strains indicate that incomplete cross-immunity generates conditions for strain-cycling behaviour at the population level. However, there have been no quantitative analyses of disease time-series that are clear examples of theoretically expected strain cycling. Here, we analyse a 40-year (1966-2005) cholera time-series from Bangladesh to determine whether patterns evident in these data are compatible with serotype-cycling behaviour. A mathematical two-serotype model is capable of explaining the oscillations in case patterns when cross-immunity between the two serotypes, Inaba and Ogawa, is high. Further support that cholera's serotype-cycling arises from population-level immunity patterns is provided by calculations of time-varying effective reproductive rates. These results shed light on historically observed serotype dominance shifts and have important implications for cholera early warning systems.
authors.affiliation: The Department of Ecology and Evolutionary Biology, 2019 Kraus Natural Science Building, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48109-1048, USA. kkoelle@umich.edu
authors.forename: Katia
authors.initials: K
authors.lastname: Koelle
authors.forename: Mercedes
authors.initials: M
authors.lastname: Pascual
authors.forename: Md
authors.initials: M
authors.lastname: Yunus
mesh_terms: D001459:Bangladesh / Q000453:epidemiology; D002771:Cholera / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology*; D006801:Humans; D018448:Models, Immunological; D010507:Periodicity; D012703:Serotyping; D014734:Vibrio cholerae / Q000145:classification* / Q000254:growth & development / Q000276:immunology