Rotavirus Transmission in Rural, Coastal Ecuador

Abstract

Rotavirus is a major cause of under-five mortality, particularly in the developing world, yet how it is transmitted is not well understood. How and why rotavirus spreads through populations is a critical concern for both preventing disease and reducing the burden. In this dissertation, I consider how rotavirus spreads through a region by focusing on two important processes: human travel and hydrological transport. I also examine how the introduction of the rotavirus vaccine in a remote region of Ecuador has changed rotavirus transmission, affecting both direct and indirect pathways. I use a combination of regression analysis and simulation modeling to address these questions. In chapter 2, I consider the effect of human travel on rotavirus transmission. To do so, I use longitudinal data from 15 villages in rural, coastal Ecuador to identify important determinants of travel patterns and the extent to which these variables are stable over time. I then incorporate these predictors into a regional transmission model to assess how demographic heterogeneity in travel impacts regional risk of rotavirus and the implications of this heterogeneity for disease interventions. In chapter 3, I investigate the conditions in which rotavirus can be transmitted through water sources and how this pathway depends on both temperature and local hydrologic conditions. I use previously published empirical studies of temperature and rotavirus persistence in water sources to conduct a meta-analysis relating temperature to rotavirus decay in water sources. Then, I combine the resulting temperature-decay function with data on hydrological characteristics of our Ecuador study site to build a transmission model that accounts for both direct transmission and water-mediated transmission. Using this model, I assess the importance of waterborne transmission to amplification of rotavirus infection within communities and spread of rotavirus through hydrological transport within a watershed. In chapter 4, I consider how the Rotarix vaccine has changed rotavirus transmission patterns in our study region. I combine data on rotavirus vaccination from local health posts with 10 years of data from a population based case control study and 18 months of diarrheal disease surveillance to estimate: (1) the direct effect of vaccination on the rate all-cause diarrhea, (2) the overall effect of vaccination on rotavirus infection and all-cause diarrhea both by age group and at a population level, and (3) the fraction of cases attributable to rotavirus in our study region.