Concetta Castilletti, PhD E-mail: concetta. castilletti@ inmi. it

© 2018 by EDIMES-Edizioni Internazionali Srl. All rights reserved at times far beyond the acute viremic and symptomatic phases of infection (Uraki et al., 2017). The finding that asymptomatic patients and women can transmit the disease sexually, even after a relatively long delay from symptoms onset, is very alarming (Moreira et al., 2017), as asymptomatic infections represent 80% of ZIKV-infected individuals (Petersen et al., 2016). To date, the longest reported duration of ZIKV-RNA shedding in semen is 188 days after symptoms onset (DSO), with viable ZIKV isolation up to 69 DSO (Nicastri et al., 2016). The implication of such a long persistence in ZIKV transmission is not fully acknowledged and, at the moment, the magnitude of person-to-person ZIKV transmission is underestimated and the role of sexual transmission is not yet clear. A major limitation for a better understanding of the extension of sexual transmission of ZIKV is the lack of diagnostic methods that could unequivocally identify the virus in semen samples. A recent study highlighted the differences in frequency with which ZIKV-RNA can be detected in various body fluids, with findings that may have implications for diagnostic recommendations (Paz-Bailey et al., 2017). In addition, longer persistence of ZIKV-RNA in whole blood as compared to plasma in ZIKV-infected non-human primates has been reported in the rhesus macaque model, indicating a preferential association with the cellular com-