Syndromic Surveillance for E-Cigarette, or Vaping, Product Use–Associated Lung Injury

Abstract

On August 1, 2019, the first cases of electronic cigarette (e-cigarette), or vaping, product use-associated lung injury (EVALI) were reported to the Centers for Disease Control and Prevention (CDC). 1 The cluster was an initial signal of an outbreak that by December 17, 2019, had resulted in 2506 cases involving hospitalized patients being reported to the CDC. Most patients with EVALI have been men and adolescent boys (67%), have been younger than 35 years of age (78%), and have reported using e-cigarette products containing tetrahydrocannabinol (THC) (80%). 2 To date, the investigation has focused predominantly on the prospective identification of new cases involving patients hospitalized with EVALI, following the health advisories that were first issued by the Wisconsin Department questions remain about whether EVALI is a new clinical syndrome or cases were previously occurring without detection. It is also unknown whether the 88% decrease in the number of cases reported to the CDC, from 214 persons admitted during the week of September 15 (the apparent peak of the outbreak) to 26 persons admitted during the week of November 24 (the most recent week with complete data), 4,5 represents a decrease in active case-finding by states or a true decrease in the incidence of cases. To assess previous trends and track the outbreak , the CDC and health departments used emergency department (ED) data from the National Syndromic Surveillance Program (NSSP). The national strategy to monitor ED data in real time was originally developed to detect bioterror-ism after the terrorist attacks of September 11, 2001, and subsequent anthrax attacks. 6 After a recent modernization, the NSSP was expanded to include data from 47 states (all states except Hawaii, South Dakota, and Wyoming) and Wash-ington, D.C., with participating health care facilities being eligible for federal incentives. The system captures free-text comments about the reason for the visit, discharge diagnosis codes, and demographic characteristics of the patients such as age and sex from approximately 70% of ED visits nationwide. Among all the visits reported to NSSP, which include more than 100 million ED visits annually, 74% of captured visits are reported within 24 hours, with 75% of discharge diagnoses typically added to the record within 1 week. This system allows for the syn-dromic surveillance of a wide variety of health exposures and outcomes, including previously unknown ones such as EVALI, in real time. 7 In this study, we developed queries of NSSP data (Section S1 in the Supplementary Appendix, available with the full text of this article at NEJM.org) to assess when ED visits associated with possible EVALI began to increase and whether the incidence of ED visits associated with these injuries had decreased in recent weeks. To visualize the outbreak, we overlaid time series of ED visits with data from Google searches and cases of EVALI that were reported to the CDC. Me thods Study Design Syndromic surveillance analysts at state health departments and the CDC collaborated to develop two queries of ED data. 8 We assessed ex-The New England Journal of Medicine Downloaded from nejm.org at UNIVERSITY OF LEEDS on February 29, 2020. For personal use only. No other uses without permission.