BACKGROUND: Zika virus (ZIKV) is a mosquito-borne flavivirus that can cause severe congenital birth defects in infants. Following an initial outbreak in Brazil in 2015, ZIKV spread rapidly through the Americas. Because New York City (NYC) is home to a large international community, imported ZIKV infections are a concern.
METHODS: The NYC Department of Health and Mental Hygiene (DOHMH) began surveillance activities for ZIKV starting January 1, 2016. Diagnostic testing was performed for symptomatic non-pregnant individuals and all pregnant patients with a history of exposure. Demographic and clinical characteristics were summarized for laboratory-positive patients, defined as either (1) positive ZIKV nucleic acid amplification test or (2) ZIKV IgM serology with a positive ZIKV plaque reduction neutralization test. All pregnant women with laboratory evidence of infection were monitored until delivery, at which time placental tissue and infant specimens were collected for ZIKV testing.
RESULTS: During January–October 2016, DOHMH identified 945 laboratory-positive patients diagnosed with ZIKV. The median age was 33 years (range: 0–78), 749 (79%) were female, (35%) resided in the Bronx, and 322 (34%) were pregnant at the time of infection. The large majority (96%) of patients acquired infection abroad, with a small proportion acquired congenitally or through sexual contact with a partner who traveled. The Dominican Republic (47%), Jamaica (11%), and Puerto Rico (8%) were the most common sources of travel-related cases. Patients reported traveling to countries with local ZIKV transmission most commonly to visit friends and relatives (67%) and for tourism/vacation/recreation purposes (22%). Almost all adult male and non-pregnant adult female patients were symptomatic (99%, 506/513), as testing criteria required symptoms. Among pregnant or post-partum patients, 31% (99/322) had symptoms consistent with Zika-like illness. Among symptomatic patients, common symptoms included rash (91%, 630/689), arthralgia (68%, 466/684), myalgia (64%, 394/613), fever (58%, 400/685), and conjunctivitis (47%, 323/677). Six patients (0.6%) with Guillain-Barré Syndrome were identified. Pregnant women were most often exposed to ZIKV in multiple trimesters (47%, 151/321) or exclusively in the first trimester (24%, 78/321). Among 230 completed pregnancies, DOHMH identified 207 (90%) live births and 23 (10%) elective terminations or spontaneous losses. Among the live births, 5 (2%) infants have conditions consistent with congenital Zika syndrome.
CONCLUSIONS: ZIKV infections in NYC to date are most notably from Caribbean countries and territories. Imported cases, including many pregnant women, represent a substantial burden to the healthcare system of NYC.