Laboratory Diagnosis of Zika Virus Infection

Context.-The rapid and accurate diagnosis of Zika virus infection is an international priority. Objective.-To review current recommendations, methods, limitations, and priorities for Zika virus testing. Data Sources.-Sources include published literature, public health recommendations, laboratory procedures, and testing experience. Conclusions.-Until recently, the laboratory diagnosis of Zika infection was confined to public health or research laboratories that prepared their own reagents, and test capacity has been limited. Furthermore, Zika cross-reacts serologically with other flaviviruses, such as dengue, West Nile, and yellow fever. Current or past infection, or even vaccination with another flavivirus, will often cause falsepositive or uninterpretable Zika serology results. Detection of viral RNA during acute infection using nucleic acid amplification tests provides more specific results, and a number of commercial nucleic acid amplification tests have received emergency use authorization. In addition to serum, testing of whole blood and urine is recommended because of the higher vial loads and longer duration of shedding. However, nucleic acid amplification testing has limited utility because many patients are asymptomatic or present for testing after the brief period of Zika shedding has passed. Thus, the greatest need and most difficult challenge is development of accurate antibody tests for the diagnosis of recent Zika infection. Research is urgently needed to identify Zika virus epitopes that do not crossreact with other flavivirus antigens. New information is emerging at a rapid pace and, with ongoing public-private and international collaborations and government support, it is hoped that rapid progress will be made in developing robust and widely applicable diagnostic tools.