Syndromic Surveillance and Case Identification for Varicella Among Recent Immigrants: New York City, 2023

<b>Objectives.</b> To determine utility of syndromic surveillance in improving varicella case detection during an outbreak among recent immigrants to New York City (NYC). <b>Methods.</b> During March through August 2023, the NYC Health Department received varicella reports from routine sources and syndromic surveillance from emergency department visits with varicella as a chief complaint or discharge diagnosis. Reports were reviewed to determine if individuals met criteria for confirmed or probable varicella cases and if cases were outbreak-associated. We calculated positive predictive value (PPV) and timeliness of syndromic surveillance reports and compared them with routine surveillance reports. <b>Results.</b> The health department received 639 unique varicella reports. Of 513 varicella cases, 247 (48.1%) were from syndromic surveillance alone, 194 (37.8%) from routine sources alone, and 72 (14.0%) from both sources. PPV was higher for syndromic surveillance (89.1%) versus routine surveillance (74.7%). Among 310 outbreak-associated cases, 139 were identified through syndromic surveillance (44.8%); syndromic surveillance was the only reporting source for 75 (24.2%). Syndromic surveillance was more timely than routine reporting (median = 3 days; range = 1-27 vs 5 days; range = 0-52). <b>Conclusions.</b> NYC syndromic surveillance improved varicella case detection during this outbreak. (<i>Am J Public Health</i>. 2025;115(4):575-578. https://doi.org/10.2105/AJPH.2024.307961).