I study the ecological and evolutionary dynamics of infectious disease in animal and human populations, and at the animal-human interface where novel human pathogens such as SARS or pandemic influenza can emerge. By combining theoretical models with data, I aim to deepen our understanding of fundamental principles of disease transmission and adaptation, and apply those principles to interpret observed patterns, uncover driving mechanisms, and design effective control policies. I work on a diverse range of disease-host systems, including leptospirosis in California sea lions, monkeypox in humans and wildlife in central Africa, and SARS and other emerging diseases in human populations.