Epidemiological Characteristics and Laboratory Findings of Zika Virus Cases in New York City, January 1, 2016-June 30, 2017

Background: An outbreak of Zika virus (ZIKV) began in May 2015 in Brazil and rapidly spread throughout the Americas; New York City (NYC) has a diverse population with similar to 1.8 million residents who were born in ZIKV-affected areas. Before July 24, 2017, the Centers for Disease Control and Prevention (CDC) ZIKV testing recommendations included nucleic acid amplification-based tests for serum and urine specimens collected <= 14 days of illness onset or last potential exposure, and ZIKV immunoglobulin M (IgM) assay when ZIKV RNA is not detected or for specimens collected within 2-12 weeks of illness onset or last potential exposure, followed by a plaque reduction neutralization test (PRNT). However, the New York public health laboratories and commercial laboratories tested specimens collected beyond these time frames. Methods: We analyzed 1080 noncongenital ZIKV cases in NYC residents who met the Council for State and Territorial Epidemiologist's ZIKV case definitions. Results: Among cases, 98% were travel associated, 1% were sexually transmitted, and 1% had unknown exposures; 412 (38%) cases were pregnant women. Of 672 patients with ZIKV RNA detected in serum or urine specimens, 48 (7%) tested positive >14 days after either symptom onset or last potential exposure date (range 15-99 days). Of 390 patients diagnosed based on serology alone (i.e., not tested or not detectable for ZIKV RNA), 60 (15%) had a positive ZIKV IgM and PRNT >12 weeks after symptom onset or last potential exposure date (range 85-273 days). Conclusion: Our findings correspond with CDC's updated guidance to test symptomatic pregnant women up to 12 weeks past onset of symptoms. ZIKV IgM antibody testing may also be warranted for pregnant women regardless of symptoms if their exposure occurred during their pregnancy or periconception period. Providers should understand the scope of diagnostic testing and its limitations to appropriately counsel patients, especially pregnant women.