1. CDC Estimating Seasonal Influenza-Associated Deaths.
https://www.cdc.gov/flu/about/disease/us_flu-related_deaths.htm
2. D. Iuliano, K.Roguski, H. Chang, D. Muscatello, R. Palekar, S. Tempia et al., Estimates of global seasonal influenza-associated respiratory mortality: a modelling study. Lancet 391(10127), 1285–1300, 31 Mar 2018
3. WHO Influenza, burden of disease.
http://www.who.int/influenza/surveillance_monitoring/bod/en/
4. CDC Flu symptoms and complications.
https://www.cdc.gov/flu/consumer/symptoms.htm/
5. CDC Types of Influenza Viruses.
https://www.cdc.gov/flu/about/viruses/types.htm