Sexually acquired Zika virus: a systematic review.

BACKGROUND: Zika virus (ZIKV) is transmitted to humans primarily by Aedes mosquito bites. However, circumstantial evidence points to a sexual transmission route.

OBJECTIVES: To assess the sexually acquired ZIKV cases and to investigate the shedding of ZIKV in genital fluids.

DATA SOURCES: PubMed, Scopus, Pro-MED-mail and WHO ZIKV notification databases from inception to December 2016.

SELECTION CRITERIA: Reports describing ZIKV acquisition through sex and studies reporting the detection or isolation of ZIKV in the genital fluids were included.

RISK-OF-BIAS ASSESSMENT: The risk of bias was assessed using the National Institute of Health Tool.

RESULTS: Eighteen studies reporting on sex-acquired ZIKV and 21 describing the presence of ZIKV in genital fluids were included. The overall risk of bias was moderate. Sexual transmission was male-female (92.5%), female-male (3.7%) and male-male (3.7%). Modes of sexual transmission were unprotected vaginal (96.2%), oral (18.5%) and anal (7.4%) intercourse. The median time between onset of symptoms in the index partner and presumed sexual transmission was 13 days (range 4-44 days). ZIKV RNA was detected in semen as late as 188 days (range 3-188 days) following symptom onset, and infectious virus was isolated in semen up to 69 days after symptom onset. No study reported ZIKV isolation from female genital samples, but detection did occur up to 13 days after symptom onset.

CONCLUSIONS: ZIKV is potentially sexually transmitted and persists in male genital secretions for a prolonged period after symptom onset. PROSPERO systematic review registration number CRD42016041475.