Assessing the Relative Timeliness of Ontario’s Syndromic Surveillance Systems for Early Detection of the 2009 Influenza H1N1 Pandemic Waves

Abstract

OBJECTIVES:Building on previous research noting variations in the operation and perceived utility of syndromic surveillance systems in Ontario, the timeliness of these different syndromic systems for detecting the onset of both 2009 H1N1 pandemic (A(H1N1)pdm09) waves relative to laboratory testing data was assessed using a standardized analytic algorithm. METHODS:Syndromic data, specifically local emergency department (ED) visit and school absenteeism data, as well as provincial Telehealth (telephone helpline) and antiviral prescription data, were analyzed retrospectively for the period April 1, 2009 to January 31, 2010. The C2-MEDIUM aberration detection method from the US Centers for Disease Control and Prevention's EARS software was used to detect increases above expected in syndromic data, and compared to laboratory alerts, defined as notice of confirmed A(H1N1)pdm09 cases over two consecutive days, to assess relative timeliness. RESULTS:In Wave 1, provincial-level alerts were detected for antiviral prescriptions and Telehealth respiratory calls before the laboratory alert. In Wave 2, Telehealth respiratory calls similarly alerted in advance of the laboratory, while local alerts from ED visit, antiviral prescription and school absenteeism data varied in timing relative to the laboratory alerts. Alerts from syndromic data were also observed to coincide with external factors such as media releases. CONCLUSIONS:Alerts from syndromic surveillance systems may be influenced by external factors and variation in system operations. Further understanding of both the impact of external factors on surveillance data and standardizing protocols for defining alerts is needed before the use of syndromic surveillance systems can be optimized.

Enhanced Influenza Surveillance Using Telephone Triage and Electronic Syndromic Surveillance in the Department of Veterans Affairs, 2011-2015

“…Our findings confirm previous evaluations that found moderate to high correlation and timeliness of TT data compared with ILI surveillance and international health agency–reported or laboratory-confirmed cases of influenza. 4,7,8,12,13 In 1 study, national triage call data from 17 states had a median correlation (using the Pearson correlation test) of 0.65 between call data and CDC viral isolate data, 4 whereas the correlation of VA-TT calls with CDC viral isolate data in our study was 0.82. Another study from Ireland found correlations between influenza-related TT calls and national ILI rates as high as 0.90.…”

“…With early detection of influenza a priority, nontraditional data sources (ie, absenteeism, over-the-counter drug sales, internet searches, and telephone triage [TT]) are being evaluated as additional sources of surveillance information. [2][3][4][5][6][7][8][9][10][11][12][13][14] TT is a method whereby a medical professional, usually a registered nurse, speaks with a patient or caregiver by telephone to assess the patient's symptoms or health concerns and offer medical advice. TT is an interactive process between the TT professional and the client, with the goal of directing the caller to the appropriate level of care or service in a safe and timely manner.…”

Quantification of the sensitivity of early detection surveillance

“…However, despite the existing wealth of literature, and the importance of early detection (item (d) above) for disease control, the authors have been unable to find any previous publication which deals with the quantitative evaluation of this form of surveillance, except for syndromic surveillance (see e.g. (Bedubourg & Strat, 2016; Chu et al., 2013; Faverjon, Vial, Andersson, Lecollinet, & Leblond, 2017)) and application of methodologies originally designed to demonstrate freedom (Welby et al., 2017).…”

Emergency department syndromic surveillance systems: a systematic review

“…Examples of public health process research (rather than data combining/sharing) were found across EDSyS in Canada [127][128][129]. Collaborative working across international borders was identified less often.…”