Updated 6 September 2016. This guidance has been developed to provide advice on the prevention of potential sexual transmission of Zika virus. The primary transmission route of Zika virus is via the Aedes mosquito. However, sexual transmission of Zika virus may also be possible, with limited evidence recorded in a few cases. This is of concern due to an association between Zika virus infection and potential complications, including microcephaly and Guillain-Barré syndrome.