From The Flu versus Anthrax:
Annual U.S. Deaths Due to the Flu: approximately 36,000.
Annual U.S. Deaths Due to Anthrax: approximately 1.Spending on R&D to fight Flu: $283 million.
Spending on R&D to fight Anthrax and other biological agents: $5.6 billion.
Of course, past performance is not a predictor of future performance. The flu might randomly get worse (e.g., 1918), but we know people have weaponized anthrax in the past, and someone out there is bound to be planning an anthrax-based attack on the US.