BACKGROUND: Influenza-like illness (ILI) self-reporting systems have opened a new field of participatory disease surveillance that puts the public directly into public health by crowdsourcing volunteer reports. Participatory surveillance has the potential to help better track known diseases and catch novel diseases as they emerge. Flu Near You (FNY), a collaboration between the Skoll Global Threats Fund and HealthMap of Boston Children’s Hospital, allows users in the U.S. and Canada to self-report symptoms of ILI via a website or smartphone application. Users can visualize aggregated ILI reports on a map, down to the zip code level. Data from the Centers for Disease Control and Prevention (CDC) are made available for comparison. This is the first comprehensive analysis of FNY data for the 2012-13 and 2013-14 influenza seasons.
METHODS: FNY reminds users via email or push notification to report their symptoms (or lack thereof) weekly. As of March 2014, FNY has had over 116,000 registrations with nearly 53,000 active users representing every state in the U.S. and every province in Canada. Weekly data from October 1, 2012 to March 23, 2014, restricted to the United States, were analyzed and compared with data from the CDC Outpatient Influenza-like Illness Surveillance Network (ILINet). To increase data reliability, the first report from each FNY user was dropped prior to analysis. Spearman ranked correlation coefficients were calculated to compare FNY ILI rates to CDC data. The FNY system defines ILI as fever plus cough and/or sore throat.
RESULTS: A total of 626,740 weekly reports were included for analysis, averaging 8,139 reports weekly. Total weekly reports ranged from 2,441 the week of October 1, 2012 to 20,248 the week of January 7, 2013. During the 2012-2013 influenza season, reports of ILI peaked the week of December 31st at 4.8% for FNY and one week earlier at 6.1% for CDC ILINet. During the 2013-2014 season, reports of ILI peaked the week of December 23rd for both FNY and CDC at 3.4% and 4.6%, respectively. We calculated a Spearman ranked correlation coefficient of rs=0.926 between FNY and CDC ILINet data from October 2012 to mid-March 2014.
CONCLUSIONS: Data from two influenza seasons during which FNY was fully operational show that participatory data demonstrates a strong correlation with CDC ILI data. With increased participation and continual system refinement, Flu Near You can serve as a complementary disease surveillance tool for the public health community.