Abstract
Unprotected sexual intercourse between persons residing in or traveling from regions with Zika virus transmission is a risk factor for infection. To model risk for infection after sexual intercourse, we inoculated rhesus and cynomolgus macaques with Zika virus by intravaginal or intrarectal routes. In macaques inoculated intravaginally, we detected viremia and virus RNA in 50% of macaques, followed by seroconversion. In macaques inoculated intrarectally, we detected viremia, virus RNA, or both, in 100% of both species, followed by seroconversion. The magnitude and duration of infectious virus in the blood of macaques suggest humans infected with Zika virus through sexual transmission will likely generate viremias sufficient to infect competent mosquito vectors. Our results indicate that transmission of Zika virus by sexual intercourse might serve as a virus maintenance mechanism in the absence of mosquito-to-human transmission and could increase the probability of establishment and spread of Zika virus in regions where this virus is not present.
Highlights
Unprotected sexual intercourse between persons residing in or traveling from regions with Zika virus transmission is a risk factor for infection
The primary mechanism of Zika virus transmission is through the bite of an infective mosquito [3,9,10], sexual transmission involving virus strains originating from African and Asian Zika virus phylogenetic lineages has been reported [11,12,13,14,15,16,17,18]
Recent evidence suggests that sexual transmission of Zika virus is responsible for a substantial number of infections [17,18,19] and could be a virus maintenance mechanism in the absence of mosquito-to-human transmission, as well as a mechanism by which Zika virus is introduced to virus-naive regions
Summary
Unprotected sexual intercourse between persons residing in or traveling from regions with Zika virus transmission is a risk factor for infection. The titer of infectious Zika virus in semen is unknown, RNA levels of up to 7.5–8.6 log copies/mL have been reported [13,21,24,25] These data suggest that maleto-female vaginal, male-to-female anal, and male-to-male anal transmission might occur more often than previously recognized and that persons might be exposed to a higher dose of Zika virus from sexual intercourse with an infectious man than through the bite of an infective mosquito [26,27]
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