(zē'kӘ), single-stranded RNA virus of the genus flavivirus that infects human and primates and causes a disease known as Zika fever or zika. It is primarily transmitted by the bite of a female Aedes mosquito, but an infected pregnant mother may transmit the virus to the fetus, and the virus also may, more rarely, be transmitted through sexual intercourse and bodily fluids. The symptoms of Zika fever typically include a low-grade fever accompanied by a rash, joint pain, or conjunctivitis; there also may be muscle pain, swelling of the joints in the hands or feet, headache, pain behind the eyes, and vomiting. Roughly three out of four persons infected with the virus, however, show no symptoms. In most cases there are no severe complications and the infected individual recovers fully, but in some outbreaks the disease has been associated with clusters of Guillain-Barré syndrome, in which the body's immune system attacks peripheral nerves, producing progressive muscle weakness that can…