The annual direct and indirect cost of flu in the U.S. is more than $87 billion.
Molinari, Noelle-Angelique M., Ismael R. Ortega-Sanchez, Mark L. Messonnier, William W. Thompson, Pascale M. Wortley, et al. The Annual Impact of Seasonal Influenza in the U.S.: Measuring disease burden and costs. Vaccine. 2007; 25: 5086-96. http://download.thelancet.com/flatcontentassets/H1N1-flu/epidemiology/epidemiology-14.pdf