This is a digitally-colorized transmission electron micrograph of Zika virus, which is a member of the family Flaviviridae. Virus particles, here colored red, are 40 nanometers in diameter with an outer envelope and an inner dense core. Zika virus is spread to people through mosquito bites. The most common symptoms of Zika virus disease are fever, rash, joint pain and conjunctivitis, or red eyes. The illness is usually mild with symptoms lasting from several days to a week. Severe disease requiring hospitalization is uncommon. Centers for Disease Control and Prevention photo by Cynthia Goldsmith