Laboratory Diagnosis of Zika Virus Infection

Thus far, all cases of Zika virus infection (ZVI) in the U.S. have occurred in travelers from Central and South America and the Caribbean. Clinically, ZVI can mimic dengue and chikungunya, also endemic in these areas, so laboratory confirmation of suspected cases is vital for tracking and clinical decision-making. These authors compared results of Zika virus testing of urine, serum, and saliva.

As of April 20, 2016, the Florida Department of Health Bureau of Public Health Laboratories had tested specimens from 913 cases that met ZVI testing criteria. Of these, 91 met confirmed or probable laboratory criteria. Of 70 urine specimens collected 0 to 20 days after symptom onset, 93% were positive for Zika virus RNA by real-time reverse transcriptase polymerase chain reaction (RT-PCR). Positive results were seen in urine specimens collected as early as day 1 from symptom onset; and in urine specimens collected within 5 days of symptom onset, the results were positive in 95%. Of serum specimens collected by day 5, only 56% were positive, and no serum specimen collected at or after day 5 was positive. About twice as many urine specimens as serum specimens were positive, although one patient had only a positive serum test. Saliva testing was almost as sensitive as urine testing, but no cases were positive exclusively by saliva testing. Zika virus immunoglobulin M antibody testing was ultimately positive in 74% of RT-PCR–negative serum specimens from cases with positive urine results.