This course introduces Dengue and Zika diseases which are caused by two viruses of the same family; Dengue virus and Zika virus. This course explains the biology of each virus in terms of its structure, genome organization, and replication strategy in cellular hosts. Transmission of both Dengue and Zika viruses to susceptible individuals occurs through mosquitoes as an arthropod vector. Thus, factors correlating mosquito biology, ecology, and human behaviour may contribute to the dynamics of dengue, which will be explained further in this course. The impact of both Dengue and Zika viral infections on the human immune system resulting in asymptomatic or severe clinical manifestations will also be discussed. Further, this course highlights current lab diagnosis and treatment, as well as the progress in the development of antiviral therapy and vaccine against both viruses.