Zika virus infection is a mosquito-borne infection caused by the Zika virus, a member of the genus Flavivirus in the family Flaviviridae. The infection is transmitted to humans mainly by Aedes aegypti and Aedes albopictus mosquitoes. Sexual contact has also been reported to cause infection. It can be diagnosed based on the detection of the virus from blood or urine samples, detection of the viral genes by reverse transcription polymerase chain reaction, positive conversion of immunoglobulin M or neutralizing antibodies, or a significant increase in antibody titer in paired sera. No effective antiviral drugs or vaccines are currently available. On rare occasions, individuals infected with the Zika virus subsequently develop Guillain-Barr e syndrome. In addition, pregnant women infected with the Zika virus can have an increased risk of fetal microcephaly, which has been recognized as a social problem. Finally, I summarized Zika virus infection in Japan as of June 2017.