Zika virus (ZIKV) infection was associated with sexual transmission among men engaged in risky sexual behaviors, according to a prospective study published in The Journal of Infectious Diseases.
Investigators aimed to characterize sexual behaviors associated with increased ZIKV infection risk. The effort was made to provide more data on how sexual transmission impacts the burden of ZIKV disease, primarily a mosquito-borne illness.
Researchers randomly selected participants from a previous 2015 study they had conducted in an economically disadvantaged community in Brazil on the attack rate and transmission dynamics of ZIKV via collection of prospective serosurveys.
Participants had to have had at least 2 serosurveys between March and October, 2015, and available ZIKV seroconversion results (anti-ZIKV immunoglobulin [Ig]G3), were older than 13 years of age, and had responded to investigators’ 2015 questionnaire on sexual behavior to be included. Investigators conducted follow-up surveys, in forms of household visits and interviews, on sexual behavior between February and April, 2017.
Researchers compared ZIKV infection rates with those of dengue virus (DENV) to control for mosquito exposure as a confounding factor. They used the NS1 IgG3 assay for ZIKV and DENV to differentiate between prior and recent exposures.
Of the 359 participants included, 38.4% were men, 47.4% identified as Black, the mean age was 30 years (standard deviation [SD], 16), and 57.7% were ZIKV IgG3 positive. Among the 302 participants with available DENV IgG3 results, 22.2% were positive.
Participants who reported having sex with more than 1 partner were more likely to be ZIKV positive (P =.02), as well as men who had more than 1 sexual partner compared with men with a single sexual partner (P =.04). The 12 men who reported having casual sexual encounters were also more likely to be ZIKV positive (odds ratio [OR], 5.8; 95% CI, 1.2-28.4), with 5 of them (41.7%) reported inconsistent condom use. When investigators analyzed these associations in those positive for DENV infection, none were statistically significant.
Investigators did not identify an association between sexual behaviors and ZIKV infection among women in the cohort. However, they found that women with 6 years or less of formal schooling were twice as likely to be positive for ZIKV (adjusted odds ratio [aOR], 2.1; 95% CI, 1.0-4.6; P =.05).
The study was limited by its small sample size and large confidence intervals. Investigators also noted that their results showed only correlational and not causative associations; people who avoid risky behavior in general, including risky sexual behavior, may also be more likely to take precautions against mosquito-borne infections and thus are more likely to avoid ZIKV disease.
The results of this study reveal that sexual activity plays a role in its transmission, which calls for the “inclusion of gender and behavioral differences in mathematical models of ZIKV transmission,” the study authors wrote.
The research authors also emphasized the need for better education about sexually transmitted ZIKV. They cited studies showing no difference in the frequency of risky sexual behaviors during and after the ZIKV epidemic despite the World Health Organization’s recommendation that people of reproductive age receive information about sexually transmitted ZIKV.
Aguilar Ticona JP, Baig H, Nery N Jr, et al. Risk of sexually transmitted Zika virus in a cohort of economically disadvantaged urban residents. J Infect Dis. Published online January 4, 2021. doi:10.1093/infdis/jiab001