By Carol A. Kemper, MD, FACP
Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center
Dr. Kemper reports no financial relationships relevant to this field of study.
SOURCES: [No authors listed.] MMWR. Interim guidance for Zika virus testing of urine — United States, 2016. May 13, 2016. MMWR Morb Mortal Wkly Rep. 2016;65:484.
Gourinat AC, O’Connor O, Calvez E, et al. Detection of Zika virus in urine. Emerg Infect Dis 2016;21:84-86.
Most patients with Zika virus (ZV) have asymptomatic or subclinical infection. Only about one-fifth of those infected are thought to develop symptoms of low-grade fever, arthralgia (generally the small joints of the hands and feet), myalgia, headache, retro-orbital discomfort, conjunctivitis, and — generally within three to five days — maculopapular rash. Confirmation of infection is hampered by the short period of viremia, generally lasting a few days of fever onset, making detection of ZV in the bloodstream difficult.
In 2013, French Polynesia experienced one of the larger outbreaks of ZV infection, with more than 1,400 confirmed cases. A few months later, cases of ZV infection began to appear for the first time in nearby New Caledonia. Gourinat and colleagues used this opportunity to examine paired urine and serum samples from six of these patients for ZV load, using rRT-PCR primers, comparing their results with spiked samples of stocked ZV. These investigators knew that other Flavivirus, such as Dengue and West Nile virus, may be detected in urine samples for longer periods of time than in serum. While they detected ZV in the serum of four patients (67%), three of whom had only one positive specimen, usually at day one to three of symptom onset, urine samples yielded ZV in all six subjects, and often in multiple specimens. ZV was detected out to 10 to 15 days from symptom onset in all six subjects, and one subject had positive urine for more than 30 days. Estimated viral loads in urine ranged from 0.7 – 220 x 106 copies/mL, which were higher than serum viral loads.
Based on these and other similar data, the CDC now offers a TrioPlex rRT-PCR assay for the detection of ZV in urine in select patients. Samples should be obtained within two weeks of symptom onset, and should be tested in conjunction with serum samples. Other assays, for commercial use, are in the works but will require validation and FDA approval.