Zika Virus Testing Considerations: Lessons Learned from the First 80 Real-Time Reverse Transcription-PCR-Positive Cases Diagnosed in New York State

Abstract

The performance and interpretation of laboratory tests for Zika virus (ZKV) continue to be evaluated. Serology is cross-reactive, laborious, and frequently difficult to interpret, and serum was initially solely recommended for molecular diagnosis. ZKV testing was initiated in January 2016 in New York State for symptomatic patients, pregnant women, their infants, and patients with Guillain-Barré syndrome who had traveled to areas with ZKV transmission. Subsequently, eligibility was expanded to pregnant women with sexual partners with similar travel histories. Serum and urine collected within 4 weeks of symptom onset or within 6 weeks of travel were tested with real-time reverse transcription-PCR (RT-PCR) assays targeting the ZKV envelope and NS2B genes. In this review of lessons learned from the first 80 positive cases in NYS, ZKV RNA was detected in urine only in 50 patients, in serum only in 19 patients, and in both samples concurrently in 11 patients, with average viral loads in urine a log higher than those in serum. Among 93 positive samples from the 80 patients, 41 were positive on both gene assays, 52 were positive on the envelope only, and none were positive on the NS2B only. Of the 80 infected patients, test results for 74 (93%) would have defined their infection status as not detected or equivocal if the requirement for positive results from two assay targets (two-target-positive requirement) in the initial federal guidance to public health laboratories was enforced, if urine was not tested, or if the extended eligibility time for molecular testing was not implemented. These changes facilitated more extensive molecular diagnosis of ZKV, reducing reliance on time-consuming and potentially inconclusive serology.

Antibody Responses to Zika Virus Infections in Environments of Flavivirus Endemicity

“…6. The interpretation of serological results is further complicated by the lower antibody titers in Zika disease than in dengue, perhaps because serum ZIKV loads are also very low (45).…”

Zika virus: an emerging challenge to public health worldwide

“…Blood serum is usually the preferred specimen choice for detection of ZIKV through either antibody-based serological methods or molecular diagnosis of viral RNA. But low-level viremia and collection of serum 10 days after the onset of symptoms may limit the sensitivity of molecular methods (St. George et al 2017;Theel and Hata 2018). However, the comparative analysis of different specimen types showed higher viral loads in urine samples (St. George et al 2017).…”

“…But low-level viremia and collection of serum 10 days after the onset of symptoms may limit the sensitivity of molecular methods (St. George et al 2017;Theel and Hata 2018). However, the comparative analysis of different specimen types showed higher viral loads in urine samples (St. George et al 2017). In addition to serum and urine, body fluids like amniotic fluid, saliva, cerebrospinal fluid, semen, and placental tissue can also be used as specimen for ZIKV detection (Gourinat et al 2015;Musso et al 2015b;Atkinson et al 2016;Staples et al 2016).…”

What Does the Future Hold for Yellow Fever Virus? (II)

“…As for other flaviviruses [232,233], YFV RNA can be detected in urine and semen but unfortunately, we lack reliable data on the frequency of detection of the virus in urine/semen samples. The closely related ZIKV is detected in urine with a 50-95% frequency [234][235][236][237] and in semen in up to 33% [233] of confirmed male cases. Noteworthy, prolonged detection of ZIKV RNA was reported in urine/semen as compared to serum [234,235,237,238], with semen being tested positive up to six months after the onset of symptoms [239].…”

“…The closely related ZIKV is detected in urine with a 50-95% frequency [234][235][236][237] and in semen in up to 33% [233] of confirmed male cases. Noteworthy, prolonged detection of ZIKV RNA was reported in urine/semen as compared to serum [234,235,237,238], with semen being tested positive up to six months after the onset of symptoms [239]. On this basis, it has been suggested that testing urine might improve molecular ZIKV detection [234,235].…”