Ko's research centers on the health problems that have emerged as a consequence of rapid urbanization and social inequity. He coordinates a research and training program on urban slum health in Brazil and is conducting prospective community-based studies on rat-borne leptospirosis, dengue, meningitis and respiratory infections. His research particularly focuses on understanding the transmission dynamics and natural history of leptospirosis, which is as a model for an infectious disease that has emerged in slum environments due to the interaction of climate, urban ecology and social marginalization. Current research combines multidisciplinary epidemiology, ecology and translational research-based approaches to identify prevention and control strategies that can be implemented in slum communities. Dr. Ko and his team has mobilized the public health research capacity at their site in the city of Salvador, Brazil to investigate the outbreak of Zika virus infection and microcephaly. He is also Program Director at Yale for the Fogarty Global Health Equity Scholars Program which provides research training opportunities for US and LMIC post and pre-doctoral fellows at collaborating international sites.