in october 2013 , a zikv outbreak was reported in french polynesia ( 9 ) . this was the second outbreak of zikv infection reported in the pacific region . in new caledonia , where zikv infection had never been documented , the first cases of zikv infection imported from french polynesia were confirmed by the end of november , and the first autochthonous cases were reported by mid - january 2014 . early in february 2014 , the new caledonia health authority declared an outbreak situation . by the end of august 2014 , > 1,400 cases of zikv infection clinical signs and symptoms of 6 zikv - infected patients are shown in the table . in this study , a cutaneous maculopapular rash of the trunk and extremities complete blood counts showed a discreet perturbation common in many viral infections ( mild leukopenia and thrombocytopenia associated with activated lymphocytes ) . * , negative ; + , light ; + + , moderate ; + + + , intense ; na , not available . to detect zikv in samples ( rna extracted from 200 l of serum or urine ) , we used both sets of primers / probe specific for zikv ( 11 ) . a standard curve with serial dilutions of known concentrations of a zikv virus stock was used to estimate viral load in samples . all blood samples were also tested for dengue virus and chikungunya virus by real - time rt - pcr and showed negative results . urine samples from 2 other patients were also positive for zikv , and showed a higher viral load than corresponding serum samples and were positive for 7 days ( patient 4 ) and probably > 20 days ( patient 3 ) after viremia reached an undetectable level ( figure ) . detection of zika virus in blood and urine specimens of 6 patients by using real - time reverse transcription pcr with primers / probe 1086/1162c/1107-cy5 ( 11 ) new caledonia , 2014 . a ) patient 1 ; b ) patient 2 ; c ) patient 3 ; d ) patient 4 ; e ) patient 5 ; f ) patient 6 . triangles indicate urine samples and squares indicate serum samples . the cutoff cycle threshold ( ct ) value is 38.5 , as previously reported ( 11 ) and is indicated by blue horizontal lines . black symbols indicate amplifications with ct < 38.5 , gray symbols indicate amplifications with ct 38.5 , and white symbols indicate negative amplifications . onset of disease ( day 0 ) was defined retrospectively after questioning patients about initial symptoms . partial sequences of the gene for zikv nonstructural protein were obtained ( 12 ) directly from amplification products from urine or serum samples . sequences obtained ( genbank accession nos . kj873160 and kj873161 ) had 100% identity with the sequence of a zikv strain isolated from a patient who returned from french polynesia in 2013 . as observed previously ( 9,13 ) , sequences also had 98% identity with sequences of zikv strains isolated in cambodia in 2010 and in yap in 2007 . we report the suitability of urine samples for diagnosis of zikv infection by showing that zikv rna is detectable in urine at a higher load and with a longer duration than in serum . zikv infection has been poorly described because it is a benign , self - limiting illness in most cases ( 5 ) . thus , zikv infection has probably been underdiagnosed and underreported in disease - endemic settings ( 4 ) or in returning travelers . however , if perifocal vector control is to be implemented and severe neurologic complications are to be avoided , biological confirmation of zikv infection is essential . because of the absence of specific igm - based diagnostic tests , molecular confirmation is the only method available for routine diagnosis . for zikv infection , date of onset of illness is difficult to establish because of sporadic and frequently mild fever . although rash has been reported 35 days after the febrile phase ( 6,7 ) , the 6 patients in our study had light asthenia and mild fever 23 days before the rash was observed ; these symptoms were considered indicative of disease onset . therefore , at the time the rash was observed , viremia was probably decreasing , which makes detection of virus in serum samples extremely challenging ( figure ) . other groups have reported that other flavivirus genomes , such as those of dengue virus ( 14 ) , west nile virus ( 15 ) and recently zikv ( 13 ) , can be detected in urine samples for a longer time than in serum samples . furthermore , use of urine samples for laboratory testing has some advantages , such as noninvasive sampling and ease of use . urine samples showed strongly positive results ; estimated maximum viral load was 0.7220.10 copies / ml . for all cases with sequential specimens , 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 . in our study , zikv was detected in patient serum until a rash was observed ( days 23 after disease onset ) . we observed a slight increase in zikv rna from urine over the first few days after disease onset and rash ( figure ) . we therefore attempted to isolate zikv from urine samples , but failed to cultivate infectious particles . further investigations are needed to evaluate whether live infectious zikv particles are excreted in urine , as has been observed for other arboviruses ( 15 ) . 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 . although these results need confirmation in larger cohorts , they strongly suggest the suitability of urine as a specimen for zikv detection and screening in large - scale investigations or other epidemiologic contexts ( e.g. , returning travelers ) . in industrialized regions , where local transmission of arboviruses , such as dengue virus or chikungunya virus has been reported , physicians should test patients who return from tropical regions for zikv when a case of dengue - like infection is suspected .
we describe the kinetics of zika virus ( zikv ) detection in serum and urine samples of 6 patients . 
 urine samples were positive for zikv > 10 days after onset of disease , which was a notably longer period than for serum samples . 
 this finding supports the conclusion that urine samples are useful for diagnosis of zikv infections .