Comparison of Zika virus (ZIKV) RNA detection in plasma, whole blood and urine - Case series of travel-associated ZIKV infection imported to Italy, 2016

- Detection rate of ZIKV RNA in plasma, whole blood and urine was examined.
- Testing whole blood is useful in the convalescence-phase of infection.
- Testing multiple specimen types is recommended to improve ZIKV RNA detection.

SummaryObjectivesThe capability to detect ZIKV RNA is of crucial importance for cases confirmation. However, due to the short-lived viremia, the detection of ZIKV RNA in plasma/serum is challenging for samples collected more than one week after onset of clinical illness. We compared the window time and detection rate of ZIKV RNA in different specimen types (plasma, whole blood and urine) collected simultaneously at several times post-symptom onset.MethodsWe examined the presence of ZIKV RNA in matched specimens of whole blood, plasma and urine collected in the same date (3-28 days after symptom onset) from 10 ZIKV infected patients.ResultsZIKV RNA was found in plasma as late as 10 days after symptoms onset and tested positive in all 5 (100%) and in 2 of 6 (33,3%) plasma samples collected 1-5 and 6-10 days after symptoms onset, respectively. ZIKV RNA was positive in urine through the 21st day after symptom onset; the detection rate of ZIKV RNA in urine samples was 100% (11/11) for samples collected 1-10 days from symptoms onset, decreasing at later times of sampling. The detection rate of ZIKV RNA in whole blood was comparable to that in urine samples but extended the window of detection of ZIKV RNA up to 26 days after symptom onset.ConclusionsOur results highlight the usefulness of simultaneously testing multiple specimen types in order to extend the rate and the time frame of ZIKV RNA detection, increasing the possibility of cases confirmation through direct diagnosis in convalescence-phase of infection, supplementing serological data which are often difficult to interpret.