Book Description

SARS. Ebola. Zika. COVID-19. The majority of all new infectious diseases discovered in the last decades are transmitted from animals to humans. More and more diseases have "spilled over" from wildlife to humans and escalated into pandemics, largely due to anthropogenic activities and global change, including climate change and land use change. Emerging diseases in wildlife can spill over from one species to another, decimating many vulnerable species. However, because human and wildlife systems are so complex, we still lack a clear understanding of the mechanisms driving disease emergence. My dissertation fills some critical gaps in our understanding of the ecological and evolutionary drivers of infectious diseases within and across species. In Chapter 1, I showed how temperature, rainfall and susceptible population size (ecological drivers) affect the (re)emerging mosquito-borne disease dengue. I used a data-driven approach for inferring causal relationships in nonlinear systems and demonstrated that suitable climate can only promote epidemics when the susceptible population is sufficiently large. In Chapter 2, I uncovered ecological and evolutionary drivers of pathogen sharing between different species using datasets of organisms and their pathogens, and their ecological and phylogenetic similarities, to understand how pathogens have adapted to multiple organisms. Here, I quantified the relative importance between ecological and evolutionary factors for predicting pathogen sharing by taxonomic level. Finally, Chapter 3 highlights a wildlife disease case study using genomic analyses of canine distemper virus (CDV) sampled from different carnivores in Alaska and Yellowstone to understand how viruses evolve in wildlife and what disease dynamics they cause. All these findings will help facilitate more effective preventative disease management strategies to improve human and animal health. In sum, my dissertation will help bridge the knowledge gap between ecological and evolutionary drivers of infectious diseases to better understand spillover and subsequent outbreaks. My research will help lay the foundation for future interdisciplinary studies in disease ecology and molecular evolution and will improve the effectiveness of both public health strategies and wildlife conservation.