1. Centers for Disease Control and Prevention20162017-06-07Seasonal Influenza-Associated Hospitalizations in the United States
http://www.cdc.gov/flu/about/qa/hospital.htm
2. World Health Organization20142017-06-06Influenza (Seasonal): Fact sheet no. 211
http://www.who.int/mediacentre/factsheets/fs211/en/
3. Centers for Disease Control and Prevention20172017-06-06Influenza (flu)
https://www.cdc.gov/flu/
4. Centers for Disease Control and Prevention20162017-06-06Overview of influenza surveillance in the United States
https://www.cdc.gov/flu/weekly/overview.htm
5. Enhancing disease surveillance with novel data streams: challenges and opportunities