Zika virus is primarily spread to people through the bite of an infected mosquito.
Many people who get infected never have symptoms. In people who get sick, symptoms (fever, rash, joint pain, and red eyes) are usually mild and resolve completely.
Zika can cause serious birth defects in babies born to women who were infected with Zika virus during pregnancy. Zika has also been linked to Guillain-Barré syndrome (GBS), a rare disorder that can cause muscle weakness and sometimes paralysis. Most people fully recover from GBS, but some have permanent damage and, in some cases, people have died.
Zika can be passed through sex from a person who has Zika to his or her partners. Zika can be passed through sex, even if the infected person does not have symptoms at the time.
Because there is no vaccine or treatment for Zika, people living in or traveling to areas with Zika should take steps to prevent infection.