The Flaviviridae are a family of positive, single-stranded, enveloped RNA viruses. They are found in arthropods, (primarily ticks and mosquitoes), and can occasionally infect humans.

Members of this family belong to a single genus, Flavivirus, and cause widespread morbidity and mortality throughout the world. Some of the mosquitoes-transmitted viruses include: Yellow Fever, Dengue Fever, Japanese encephalitis, West Nile viruses, and Zika virus. Other Flaviviruses are transmitted by ticks and are responsible of encephalitis and hemorrhagic diseases: Kyasanur Forest Disease (KFD) and Alkhurma disease, and Omsk hemorrhagic fever.

Digitally-colorized transmission electron micrograph of the West Nile virus, in the flavivirus family.