Relationship Between Baseline Influenza-like Illness Rates And Healthcare Settings
Authors: Rumoro Dino , Shah Shital , Gibbs Gillian , Hallock Marilyn , Trenholme Gordon , Waddell Michael 
Published: May 2017

ObjectiveTo examine the baseline influenza-like illness (ILI) rates in theemergency departments (ED) of a large academic medical center(AMC), community hospital (CH), and neighboring adult andpediatric primary care clinics.IntroductionThe primary goal of syndromic surveillance is early recognitionof disease trends, in order to identify and control infectious diseaseoutbreaks, such as influenza. For surveillance of influenza-like illness(ILI), public health departments receive data from multiple sourceswith varying degrees of patient acuity, including outpatient clinicsand emergency departments. However, the lack of standardization ofthese data sources may lead to varying baseline levels of ILI activitywithin a local area.MethodsGeographic Utilization of Artificial Intelligence in Real-Timefor Disease Identification and Alert Notification (GUARDIAN) – asyndromic surveillance program – was used to automate ILI detectionusing free text chief complaint/reason for visit fields and vital signsfor a large AMC - ED, CH - ED, and neighboring outpatient clinicsduring the summer (June 15, 2016 to August 18, 2016) in order tocreate a baseline. The GUARDIAN system defined ILI as fever(temperature≥100°F) and cough and/or sore throat. Descriptiveanalysis of the observed ILI rates along with bivariate ANOVA withpost hoc Bonferroni and t-test were utilized to examine the differencewithin the settings.ResultsThe average ILI rate for EDs is higher than the clinics by at least0.39%. The CH- ED had 4.23% baseline ILI rate as compared to1.35% for AMC-ED. While the AMC – Clinics have 0.96% baselineILI rate as compared to 0.25% for CH – Clinics. The CH- ED andAMC – Clinics represented higher variations. Based on bivariate test,CH – ED was significantly different than AMC – ED, AMC - Clinics,and CH – Clinics (F= 10.58, df = 1238, p<0.05). For the AMC –Clinics, the average ILI rate for clinics providing services to adultpatients was 0.66% (SD: 4.5%) as compared to 2.03% (SD: 10.81%)for pediatric clinics, which was not statistically significant.ConclusionsThe CH - ED has higher baseline ILI rates compared to othersettings, as well as the CDC Region 5’s baseline (1.9% for 2015-2016). Based on previous studies1, this is likely due to providers’use of chief complaint free text fields. Thus, the CH – ED will havehigher thresholds for widespread ILI activity. In addition, differencesin baseline ILI rates between AMC - ED, AMC - Clinics, and CH -Clinics may result in different thresholds for widespread ILI activity(i.e., Average + 3 Standard Deviations). The CH – ED and AMC –Clinics had higher baseline standard deviations, indicting variationsin underlying patient populations. In addition, pediatric clinics havehigher baseline ILI activity but also higher variations, indicating theunique characteristics of pediatric patients. Thus, due to the abovefindings, there is a need to closely monitor the ILI rates at varioushealthcare sites for both timing of onset, as well as the intensity ofILI activity.