My primary research focuses on developing statistical methods for transmission dynamics of infectious diseases such as influenza, dengue, Ebola, COVID-19, HIV and cholera at both individual and population levels. These methods are designed to evaluate transmissibility of pathogens, efficacy of interventions, and effects of risk factors in various study settings. Examples are studies with case-ascertained follow-up, competing risks of infection from co-circulating pathogens or strains, and high-dimensional missing data. I developed methods for assessing vaccine or antiviral efficacy when there was only a small number of laboratory-tested specimens. I am also interested in modeling co-circulating of multiple pathogens with cross-reactivity, e.g., dengue viruses and enteroviruses, especially when the underlying exposure history is incompletely observed. In response to the ongoing COVID-19 pandemic, I have been engaged in multiple collaborative projects of analyzing contact-tracing data, case incidence data and lab-testing data. My long-term goals in methodological research are to integrate phylodynamics and AI methods into transmission modeling and to address surveillance bias. See my CV for lists of publications and grants.