Zika virus is a mosquito-borne flavivirus. The virus is transmitted through the bite of an infected Aedes mosquito, mainly Aedes aegypti, in tropical and subtropical regions. The same mosquito also transmits the viruses causing dengue, chikungunya and yellow fever. Zika virus is also transmitted from mother to fetus during pregnancy, through sexual contact, transfusion of blood and blood products, and organ transplantation.

The incubation period (the time from exposure to symptoms) of Zika virus disease is estimated to be 3–14 days. Symptoms are similar to other arbovirus infections, and include fever, skin rashes, conjunctivitis, muscle and joint pain, malaise, and headache. These symptoms are usually mild and last for 2-7 days and often do not require any specific treatment. However, Zika virus infection during pregnancy is a cause of microcephaly and other congenital abnormalities in the developing fetus and newborn and can lead to pregnancy complications such as fetal loss, stillbirth, and preterm birth. Zika virus was shown to be a trigger of the Guillain-Barré syndrome neuropathy and myelitis, particularly in adults and older children. Zika virus infection can only be confirmed by laboratory tests of blood or other body fluids, such as urine or semen.