Zika virus disease is caused by the Zika virus, which is spread to people by mosquito bites. An estimated 80% of people who get Zika have no symptoms. When symptoms appear, they are usually mild, last a few days to a week, and go away on their own. The most common symptoms are fever, rash, joint pain, and red eyes. Although most Zika infection is spread by mosquito bites, it can also be spread from mother to child in pregnant women and can be sexually transmitted. There is currently no treatment for Zika.