Dr. Ruan focuses his research efforts on 1) modeling the interaction of tumor cells and immune system and hematopoiesis process with applications to chronic myelogenous leukemia; and 2) Modeling transmission dynamics of some infectious diseases (for instance, malaria, Rift Valley Fever in Egypt, Hepatitis B virus, Schistosomiasis, human rabies, West Nile virus, dengue, Zika, etc.) and antibiotic-resistant bacteria infection in hospital and community.