Little is known about asymptomatic infections and viraemia.
A decent number of studies have shown that urine may be a better sample for testing using molecular methods because of prolonged viral shedding (viruria) and sometimes higher viral load compared to serum samples.
The following is a list of some of the peer-reviewed literature and some public health advisories that have mentioned seeking ZIKV in urine using molecular techniques.
Australian Department of Health
Blood & Urine: 1st 14 days post symptom onset
http://www.health.gov.au/internet/main/publishing.nsf/Content/ohp-zika-health-practitioners.htm#toc05
European CDC
Blood: 3-5d post
onset
Urine: up 10 10d
Public Health England
Blood: Anyone with travel history and current/past symptoms suggetsing ZIKV infection
Urine: Pregnant woman with current symptoms/male with current symptoms and a pregnant partner
https://www.gov.uk/guidance/zika-virus-sample-testing-advice
United States CDC
Serum\CSF: Must be collected as primary test
substrate
Urine: Can also be
submitted
Kutsuna et al
In
1/2 cases, ZIKV RNA detected in urine when serum negative
Gourinat et al
Detected
in urine of 6/6 symptomatic patients between 10 to 20 days after onset (7-20d
better than serum), often with higher viral loads from urine samples than from
serum. Serum positive in 4/6 but only until rash observed (2-3d post onset).
Urine levels rise slightly after disease and rash onset - “preferred for virus
detection”.
Shinohara et
al
ZIKV
RNA detected in urine 7 days after symptom onset; serum equivocal at 2 days
post-onset
Besnard et al
Urine
positive in 2 cases up to 8 days post-onset, in one case after serum was
negative
Brasil et al
Of
88 women, 72 (82%) had positive results for ZIKV on PCR in blood, urine, or
both; 60 in serum specimens; 46 in urine samples; 34 in both specimens; 12 in
urine specimens only; 26 in blood specimens only; median number of PCR cycles
for serum specimens - 33.0; median number of PCR cycles for urine specimens -
29.0.
Roze et al
Urine
positive in 2/2 cases when serum was negative. 15-21 days after neurological
symptom onset.
Barzon et al
Urine
and had 106-fold higher viral loads than serum. Both sample types
positive from 5 days after symptom onset, Urine positive until 22 days after
onset-saliva until 29 days.
The outcome here is that urine is a sample that looks like it should be requested perhaps much more often than it is. Also, the language around recommending the collecting of urine is not as clear as it appears that it should be - including by some other public health agencies
As it stands, a negative serum RT-PCR test for ZIKV does not hold a lot of meaning because of the narrow detection window using blood.
Urine has proven itself useful for detection and confirmation of ZIKV infection - a process that is key to learning more about the virus and its impact(s) on infected humans.
Use urine. Welcome the wee. Take the...well you get the point.
