More widespread testing for Zika virus is now available, as the FDA recently issued an Emergency Use Authorization (EUA) for a Qualitative Real-Time RT-PCR test.
In addition, the CDC recently announced a urine test that can detect the virus for up to two weeks. 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 two weeks after onset of symptoms, the CDC noted. Currently, the CDC Trioplex rRT-PCR assay is the only diagnostic tool authorized by the FDA for Zika virus testing of urine. Other laboratory-developed tests will need in-house validations to adequately characterize the performance of the assay and meet Clinical Laboratory Improvement Amendments requirements. Further investigation is needed to determine the sensitivity and utility of Zika virus rRT-PCR on urine specimens collected ≥14 days after onset of symptoms.
On the basis of the newly available data, the 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. Procedures for the collection and submission of body fluids, including urine specimens, have been described previously. CDC recommendations for Zika virus testing of serum and other clinical specimens remain unchanged at this time. CDC will continue to review and update guidance for Zika virus testing as new data become available.
Developed by Focus Diagnostics Inc. (a subsidiary of Quest Diagnostics in Madison, NJ), the test will detect Zika virus RNA in blood samples. The test should only be used for individuals meeting CDC virus clinical criteria (e.g., clinical signs and symptoms associated with infection) and/or CDC Zika virus epidemiological criteria (e.g., history of residence in or travel to a geographic region with active Zika transmission) by qualified laboratories designated by Focus Diagnostics, Inc., the FDA emphasized.
The EUA does not indicate formal FDA approval indefinitely, and can expire or be terminated or revoked by the Department of Health and Human Services. According to a fact sheet posted by the FDA, Zika transmission is occurring in 35 countries and territories in the Americas, seven countries and territories in Oceania/Pacific Islands, and one country in Africa.
If Zika virus infection is suspected based on current clinical and epidemiological criteria, the RT-PCR test may be ordered. As chikungunya and dengue infection can have early symptoms resembling those of Zika infection — and co-infection with these viruses is possible — testing for those viruses should be considered as well.
Zika virus RNA is typically detectable in serum for approximately seven days following onset of symptoms. Contact your state or local health department to facilitate testing, the FDA advises.
As of June 1, 2016, there were 618 travel-associated cases of Zika reported in the U.S. There were no vector-borne cases reported, but 11 cases were due to sexual transmission and there was one case of Guillain-Barré syndrome. In addition, as of May 26, 2016, there were 195 pregnant women with Zika in the U.S.
In U.S. territories, there were 146 pregnant women with Zika virus infection. There were 1,110 locally acquired cases and five travel-associated cases in the territories.
- FDA. Fact Sheet for Health CareProviders: Interpreting Zika Virus RNA Qualitative Real-Time RT-PCR Test Results. April 28, 2016: