Evaluation of an Internet-Based Monitoring System for Influenza-Like Illness in Sweden

Abstract

To complement traditional influenza surveillance with data on disease occurrence not only among care-seeking individuals, the Swedish Institute for Communicable Disease Control (SMI) has tested an Internet-based monitoring system (IMS) with self-recruited volunteers submitting weekly on-line reports about their health in the preceding week, upon weekly reminders. We evaluated IMS acceptability and to which extent participants represented the Swedish population. We also studied the agreement of data on influenza-like illness (ILI) occurrence from IMS with data from a previously evaluated population-based system (PBS) with an actively recruited random sample of the population who spontaneously report disease onsets in real-time via telephone/Internet, and with traditional general practitioner based sentinel and virological influenza surveillance, in the 2011–2012 and 2012–2013 influenza seasons. We assessed acceptability by calculating the participation proportion in an invited IMS-sample and the weekly reporting proportion of enrolled self-recruited IMS participants. We compared distributions of socio-demographic indicators of self-recruited IMS participants to the general Swedish population using chi-square tests. Finally, we assessed the agreement of weekly incidence proportions (%) of ILI in IMS and PBS with cross-correlation analyses. Among 2,511 invited persons, 166 (6.6%) agreed to participate in the IMS. In each season, 2,552 and 2,486 self-recruited persons participated in the IMS respectively. The weekly reporting proportion among self-recruited participants decreased from 87% to 23% (2011–2012) and 82% to 45% (2012–2013). Women, highly educated, and middle-aged persons were overrepresented among self-recruited IMS participants (p<0.01). IMS (invited and self-recruited) and PBS weekly incidence proportions correlated strongest when no lags were applied (r = 0.71 and r = 0.69, p<0.05). This evaluation revealed socio-demographic misrepresentation and limited compliance among the self-recruited IMS participants. Yet, IMS offered a reasonable representation of the temporal ILI pattern in the community overall during the 2011–2012 and 2012–2013 influenza seasons and could be a simple tool for collecting community-based ILI data.

High added value of a population-based participatory surveillance system for community acute gastrointestinal, respiratory and influenza-like illnesses in Sweden, 2013–2014 using the web

“…Recognizing these limitations, Sweden has tested and evaluated telephone- and web-based population-based surveillance [ 4 , 5 ], but this effort was limited in the number of syndromes possible to include and its ability to add questionnaires. To enable feasible population-based surveillance of a broader spectrum of syndromes with the flexibility to add questionnaires, such as on disease severity, the PHAS set up Hӓlsorapport, a population-based surveillance system that entirely relies on symptoms reported over the web.…”

Ten-year performance of Influenzanet: ILI time series, risks, vaccine effects, and care-seeking behaviour

“…In this context, new approaches in syndromic surveillance -the collection and interpretation of data for public health before laboratory or clinical confirmation is available (Lazarus et al, 2001;Mandl et al, 2004) -have emerged. Several systems are in evaluation, showing a large diversity of data sources and methodologies employed, such as telephone-based health information services (Cooper et al, 2008), automated medical records (Lazarus et al, 2001;van den Wijngaard et al, 2008), pharmacy sales and absenteeism (Chretien et al, 2008), queries to online search engines (Ginsberg et al, 2009), and telephone-based self-reporting in cohorts of randomly selected participants (Merk et al, 2013;Rehn et al, 2014). Syndromic surveillance is complementary to traditional public health surveillance in disease reporting (Henning, 2004;Lipsitch et al, 2009).…”

The potential value of crowdsourced surveillance systems in supplementing sentinel influenza networks: the case of France

“…This suggests that self-reported digital data collected directly from the general population and analysed in a timely fashion can considerably reduce the time needed to produce sentinel estimates (that needs to account for the delay for consulting a primary care doctor and centralising sentinel data for analysis). Confirmed by other participatory systems [ 11 , 13 - 15 , 33 ], this feature may function as an important alert system for public health preparedness before reaching the highest weekly incidence value.…”