Zika fever is caused by a viral Zika infection, which is a member of the virus family Flaviviridae, and is thus related to the dengue, yellow fever, and West Nile viruses. And Zika virus is enveloped and icosahedral and has a nonsegmented, single-stranded, 10 kilobase positive-sense RNA genome. A positive-sense RNA genome can be directly translated into viral proteins. As in other flaviviruses, such as the similarly sized West Nile virus, the RNA genome encodes seven nonstructural proteins and three structural proteins. One of the structural proteins encapsulates the virus. The RNA genome forms a nucleocapsid along with copies of the 12 kDa capsid protein.