Presence and Persistence of Zika Virus RNA in Semen, United Kingdom, 2016

Abstract

Zika virus RNA has been detected in semen collected several months after onset of symptoms of infection. Given the potential for sexual transmission of Zika virus and for serious fetal abnormalities resulting from infection during pregnancy, information regarding the persistence of Zika virus in semen is critical for advancing our understanding of potential risks. We tested serial semen samples from symptomatic male patients in the United Kingdom who had a diagnosis of imported Zika virus infection. Among the initial semen samples from 23 patients, Zika virus RNA was detected at high levels in 13 (56.5%) and was not detected in 9 (39.1%); detection was indeterminate in 1 sample (4.4%). After symptomatic infection, a substantial proportion of men have detectable Zika virus RNA at high copy numbers in semen during early convalescence, suggesting high risk for sexual transmission. Viral RNA clearance times are not consistent and can be prolonged.

Keywords: RNA; United Kingdom; Zika; Zika virus; flavivirus; infectious diseases; mosquitoborne; persistence; semen; sexual transmission; vector-borne infections; viruses.

Figure

Cycle threshold (C_t) values of semen samples analyzed to determine presence and persistence of Zika virus RNA in semen, United Kingdom, 2016. All references to days indicate days after onset of symptoms. The dotted line represents the limit of detection for the assay. The lines represent implied decay rates based on longitudinal data; however, they should not be used to infer exact data between analyzed samples. In particular, the point at which viral RNA became undetected cannot be accurately inferred from the curves for patients 5, 8, 9, and 10. Patient 6 had a previous vasectomy, and patient 8 was receiving immunosuppressive drug therapy at the time of sampling. IND, indeterminate; NA, not available.