Sexual transmission of Zika virus enhances in utero transmission in a mouse model.

Zika virus (ZIKV) is an emerging mosquito-borne virus that can cause ZIKV congenital syndrome when a pregnant woman is infected. Sexual transmission has also been described for ZIKV, though the relationship between sexual transmission and vertical transmission has not been investigated. Here, viral dissemination to the female reproductive tract and fetuses was assessed in immunodeficient (AG129) female mice that were exposed to ZIKV by subcutaneous (s.c.) inoculation, intravaginal (ivag.) inoculation, or sexual transmission from infected male AG129 mice. Pregnant females had significantly increased ZIKV dissemination to the female reproductive tract compared to non-pregnant females when exposed by s.c. or ivag. inoculation. Sexual transmission resulted in significantly greater morbidity and mortality in females and higher ZIKV titers in the female reproductive tract than s.c. or ivag. inoculation. Ovaries from females infected sexually contained ZIKV RNA within the ovarian follicles. Furthermore, ZIKV titers were significantly higher in fetuses from dams exposed sexually compared to fetuses from dams exposed by s.c. or ivag. inoculation. These results demonstrate that sexual transmission enhances dissemination of ZIKV to the female reproductive tract and developing fetuses in a mouse model.