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Flu Near You, local data for local action

Posted By Eric Bakota, Monday, June 26, 2017
Updated: Monday, June 26, 2017

I first became aware of Flu Near You (FNY) from a colleague while I worked at my previous job at the Tazewell County Health Department (TCHD) in central Illinois. I was the epidemiologist for the County, which housed roughly 135,000 residents. At TCHD, I was less of an epidemiologist than a general ‘data & technology’ guy. There just wasn’t enough local data to do proper epidemiological analyses. Our data was too sporadic, too sparse and too noisy. We regularly were frustrated by this problem, but accepted it as a fact of life for being in a county that didn’t have a million people.

FNY works by transforming a regular citizen into a citizen scientist. Every Monday, these citizen scientists collect the previous week’s health data about themselves and their families. They then transmit the data through the web or through the FNY smartphone app. This data is then aggregated and analyzed to determine influenza-like illness trends for states and the nation by the team at HealthMap at Boston Children's Hospital, which runs FNY. These analyses have been shown to be very consistent with CDC estimates of influenza-like activity1 .

Local and State Health Departments can easily and quickly gain access to these data. HealthMap has committed itself to sharing the de-identified data widely in the hopes that the data can lead to positive public health action. After being given access to the data, I wanted to see how many users were necessary to gain a good signal that still correlated to CDC’s ILINet data. At over 10,000 weekly participants, the data correlates very, very well (R ~ 0.96). I conducted the same analysis with 1,000 weekly participants and was surprised to see that the correlation continued to be very strong (R ~ 0.88). At 500 participants, it was still strong (R ~ 0.80). It wasn’t until approximately 200 weekly participants or fewer that the signal started dropping off and becoming unreliable.

The major conclusion from this analysis was that a local health department only needed to find 200 individuals willing to participate for this tool to be worthwhile within its jurisdiction. For most areas, this will require some active recruiting efforts, but I believe it is achievable. Once an area has reached the 200 mark, I believe public health officials can interpret FNY data with enough confidence for it to trigger public health action – say a news alert stating that influence has spiked within the county and encouraging the public to get vaccinated.

Flu Near You is tool that transforms regular people into citizen scientists

FNY, ILINet, and CDC Virological data, transformed by scaling each value as a proportion of the peak value, correlate very tightly with each other.

Correlation between bootstrapped samples of FNY estimated percent ILI and observed percent ILI, as reported by the CDC (grey), and laboratory confirmed influenza cases (red) at the national resolution with 95% Confidence Intervals for the 2014-2015 flu season.

Flu Near You is a participatory disease surveillance system for volunteer reports of ILI symptoms that was created in 2011 by APHA, HealthMap of Boston Children’s Hospital, and the Skoll Global Threats Fund (SGTF). In 2016, CSTE and SGTF partnered to further explore the utility of Flu Near You data as a novel data source for influenza surveillance in the state and local health department setting. For more information, please contact mschroeder@cste.org.


Eric Bakota, MS is a staff analyst in the Office of Surveillance and Public Health Preparedness at the Houston Health Department. Eric is currently a CSTE Informatics-Training in Place Fellow.

1Smolinski MS, Crawley AW, Baltrusaitis K, et al. Flu Near You: Crowdsourced Symptom Reporting Spanning 2 Influenza Seasons. American Journal of Public Health. 2015;105(10):2124-2130. doi:10.2105/AJPH.2015.302696

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