A disease caused by the Zika virus that is transmitted primarily through the bite of an infected Aedes mosquito, the species that also spreads dengue and yellow fever. The most common symptoms are fever, rash, joint pain and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting for several days to a week. The virus can also be transmitted from a mother to her baby during pregnancy or around the time of birth. There have been reports of a serious birth defect of the brain called microcephaly (a condition in which a baby's head is smaller than expected when compared to babies of the same sex and age) and other poor pregnancy outcomes. Knowledge of the link between Zika and these outcomes is evolving. The virus can also be spread by sexual contact.