Arboviruses are generally transmitted by small biting insects such as mosquitoes. These insects are not just passive carriers of the viruses, but are required by the viruses to complete their life cycles. So arboviruses cannot pass directly from one victim to another except rarely by transfusion of contaminated blood or transplantation of an infected organ. Nevertheless, these viruses are spreading widely, causing large epidemics in humans and domestic animals, with increasing morbidity, mortality, and severe economic implications. ‘Emerging virus infections: arthropod-transmitted viruses’ describes the yellow fever, Zika, Chikungunya, West Nile, dengue fever, and Rift Valley viruses. As the emergence and re-emergence of viruses is increasing, vaccines to protect both humans and domestic animals and to prevent virus spread are urgently needed.