Due to the fact that currently no commercial tests allowing for the serological diagnosis of ZIKV infection are available, ZIKV acute infection may be diagnosed by RT-PCR (reverse transcription polymerase chain reaction) directly from virus RNA in patient's serum, preferably obtained up to the sixth day of disease.
In this article named "Detection of Zika virus in saliva", they found that during the French Polynesian outbreak, several patients presenting the major symptoms of Zika fever were tested negative by Zika virus RT-PCR in blood collected during the first week after symptoms onset.
Zika virus was more frequently detected in saliva compared to blood. For the 182 patients with both samples collected, tests were positive for 35 (19.2%) in saliva while negative in blood and tests were positive for 16 (8.8%) in blood while negative in saliva; the difference in mean days after symptoms onset and the percentage of the main symptoms of Zika fever for patients only positive in saliva or in blood was not significant.
The use of saliva sample increased the rate of molecular detection of ZIKV at the acute phase of the disease but did not enlarge the window of detection of ZIKV RNA. Saliva was of particular interest when blood was difficult to collect (children and neonates especially).
In this article named "Detection of Zika virus in urine", they said biological confirmation of ZIKV infections is based mostly on detection of virus RNA in serum by using reverse transcription PCR (RT-PCR). Although IgM against ZIKV can be detected by ELISA, few laboratories have this ability. Thus, in addition to the nonspecific clinical features of infection with ZIKV, laboratory diagnosis is challenging because of low viremia and cross-reactivity of ZIKV antibodies with other flaviviruses (including dengue), which require confirmation by neutralization assays and make rapid serologic confirmation difficult. So, they investigated the diagnostic utility of urine as a source for detection of ZIKV RNA by real-time RT-PCR. They also found that ZIKV RNA is detectable in urine at a higher load and with a longer duration than in serum. Urine samples showed strongly positive results.
ZIKV RNA was detected ≤15 days (range 10 days to >20 days) after onset of symptoms, which was >7 days after it was not detected in serum samples. ZIKV was detected in patient serum until a rash was observed (days 2–3 after disease onset). However, urine was preferred for virus detection. We observed a slight increase in ZIKV RNA from urine over the first few days after disease onset and rash.
This study investigated the diagnostic utility of urine as a source for detection of ZIKV RNA by real-time RT-PCR. Results suggest that urine might be useful for confirmation of ZIKV infection because virus was detected at higher titers and for a longer period in urine samples than in serum samples.