Infectious Diseases
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Study examines risk estimation of sexual transmission of Zika virus

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Although the risk of Zika virus (ZIKV) transmission through unprotected sex is low, the potential impact ZIKV infection can have, particularly for pregnant women, is significant, according to a study.

In this study, data from the U.S. national arboviral disease surveillance system (ArboNET) on travel- and sexually-acquired ZIKV disease cases during 2016–2017 were used to estimate the risk of sexual transmission of ZIKV by determining ZIKV RNA persistence in semen/vaginal fluids to approximate infectiousness duration.

The highest estimated probability was for male-to-male transmission (1.3% per anal sex act) followed by male-to-female (0.4% per vaginal/anal sex act) and female-to-male transmission (0.1% per vaginal sex act).

When viral isolation in semen versus RNA detection to approximate infectiousness duration was used, a greater risk of sexual transmission was predicted.

“While likely insufficient to maintain sustained transmission, the estimated risk of ZIKV transmission through unprotected sex is not trivial and is especially important for pregnant women, as ZIKV infection can cause severe congenital disorders,” the authors concluded.

Major CG, Paz-Bailey G, Hills SL, et al. Risk estimation of sexual transmission of Zika virus—United States, 2016–2017. J Infect Dis. 2021; jiab173, https://doi.org/10.1093/infdis/jiab173