Dr. Eva Harris: Dengue and Zika are mosquito-borne viral diseases that consitute major public health and medical problems worldwide. Dengue has been a scourge for decades and only continues to increase in magnitude, geographic distribution, and severity, whereas Zika recently took the world by surprise with a dramatic epidemic in the Americas that was linked to severe congenital defects, including microcephaly, when infection occurred during pregnancy. In this lecture, “Migration of dengue and Zika viruses: Across continents, around cities, and within the human host”, we will explore the concept of “migration” as applied to dengue and Zika on multiple levels. First, we will examine the emergence and spread of these viruses seen through both epidemiological and phylogenetic lenses, through studies of human populations and viral sequences. Next, we will focus on spatial studies of dengue and Zika transmission in our cohort study of children in Managua, Nicaragua, where we have observed differences in Zika virus transmission at a hyper local level, allowing identification of hot-spots and environmental risk factors. Finally, we will turn to “migration” of dengue and Zika viruses within the human body, via studies of intrahost diversity of these RNA viral sequences in different bodily compartments as well as visualization of Zika virus invasion of the human placenta. Through this unusual interpretation of the concept of migration, we hope to introduce multiple themes in research and public health of these important human infectious diseases.