BACKGROUND: Zika virus (ZIKV) infection during pregnancy can cause microcephaly and other severe birth defects in exposed infants. Laboratory diagnosis of ZIKV infection in pregnant women can inform pregnancy management, identify exposed infants, and influence their care. In New York City (NYC) in early February 2016, ZIKV testing was recommended for all pregnant women who traveled to a country with active ZIKV transmission (ZIKV country) or had sex without a condom with a partner who traveled to a ZIKV country. We assessed area-level differences in ZIKV testing and incidence among women of childbearing age (WCBA) in NYC by census tract immigrant number and poverty level.
METHODS: Home addresses of NYC patients tested for ZIKV during January–July 2016 were geocoded to census tracts and classified by poverty level and quartile of the number of immigrants from ZIKV countries per the American Community Survey 2010–2014. Testing and incidence rates of ZIKV laboratory-positive cases were calculated for WCBA. We ranked NYC birth hospitals by the number of deliveries during 2011–2016 to women born in a ZIKV country to identify facilities potentially caring for larger populations at risk for ZIKV exposure.
RESULTS: During January–July 2016, 4,733 WCBA underwent ZIKV testing. During January–February, WCBA living in census tracts in the highest quartile of immigrants from ZIKV areas were less likely to be tested than those in the lowest quartile (15 vs. 52 per 100,000 WCBA; relative risk: 0.29; 95% confidence interval: 0.25–0.35). By June–July 2016, after outreach to reduce barriers and encourage ZIKV testing targeted to providers and birth hospitals serving immigrants from ZIKV countries, testing increased in areas with the largest immigrant populations (51 per 100,000 WCBA). Cumulative ZIKV incidence was higher in census tracts with the largest versus smallest immigrant populations (37 vs. 3/100,000 WBCA) and with the highest versus lowest poverty levels (28 vs. 13/100,000 WCBA). The highest cumulative ZIKV incidence rates were in areas with both large immigrant populations and high poverty (39/100,000 WCBA).
CONCLUSIONS: Communities with large immigrant populations and higher poverty levels were at higher risk for imported ZIKV cases. The lower rates of ZIKV testing initially observed in these communities suggested testing disparities and were helpful in targeting interventions. Testing rates increased in higher risk groups, and the observed differences did not persist. Public health emergency responses can use data successfully to identify and remediate disparities in testing and disease incidence.