Steve Halasey, CLP.
If there is a single characteristic that has distinguished early research into the etiology and epidemiology of the Zika virus, it is that nothing known about the virus can be relied upon to be true beyond the results of the next set of studies.
At almost every turn, researchers and public health authorities who are studying and continuing to track the emergence and spread of the Zika virus in the Western Hemisphere have been surprised by new study findings, sometimes completely overturning previously accepted views. The latest surprise, based on a study conducted at the Florida Department of Health Bureau of Public Health Laboratories, refines thinking of the Centers for Disease Control and Prevention (CDC) about what sample types are suitable for testing, and when.1 According to interim guidance issued by CDC at the beginning of May:
Real-time reverse transcription–polymerase chain reaction (rRT-PCR) is the preferred test for Zika virus infection because it can be performed rapidly and is highly specific. However, in most patients, Zika virus RNA is unlikely to be detected in serum after the first week of illness. Recent reports using adaptations of previously published methods suggest that Zika virus RNA can be detected in urine for at least 2 weeks after onset of symptoms.2
The Florida study examined saliva, serum, or urine specimens collected from patients with confirmed or probable cases of Zika disease on days zero to 20 after the onset of symptoms. In one evaluation of 66 patients’ paired serum and urine samples collected on the same days, approximately twice as many patients had positive RT-PCR test results from urine specimens (92%) as those who had positive results from serum specimens (47%). These and other findings from the Florida study have led CDC to alter its recommendations for Zika virus testing, especially during the early, viremic phase of Zika virus infection.
On the basis of the newly available data, CDC recommends that Zika virus rRT-PCR be performed on urine collected <14 days after onset of symptoms in patients with suspected Zika virus disease. Zika virus rRT-PCR testing of urine should be performed in conjunction with serum testing if using specimens collected <7 days after symptom onset. A positive result in either specimen type provides evidence of Zika virus infection.2
Currently, only CDC’s own Trioplex rRT-PCR assay has been granted FDA emergency use authorization for testing of urine specimens. But CDC acknowledges that further investigation will be needed to determine the sensitivity and utility of rRT-PCR tests on urine specimens collected ?14 days after the onset of symptoms.
Now, where did I put my copy of the next Zika study?
Steve Halasey
Chief Editor, CLP
[email protected]
(626) 219-0199
REFERENCES
- Bingham AM, Cone M, Mock V, et al. Comparison of test results for Zika virus RNA in urine, serum, and saliva specimens from persons with travel-associated Zika virus disease, Florida, 2016. Morb Mortal Wkly Rep. 2016;65; Early release, May 10, 2016; doi: http://dx.doi.org/10.15585/mmwr.mm6518e2.
- Interim guidance for Zika virus testing of urine, United States, 2016. Morb Mortal Wkly Rep. 2016;65; Early release, May 10, 2016; doi: http://dx.doi.org/10.15585/mmwr.mm6518e1.
