The 2001 United States Anthrax Attacks were a series of bioterrorism incidents that occurred shortly after the September 11 attacks. Letters containing anthrax spores were mailed to several news media offices and two Democratic Senators, Tom Daschle and Patrick Leahy, resulting in five deaths and 17 infections. The letters included messages warning against the United States' actions in the Middle East. The FBI launched an extensive investigation, known as Operation Anthrax, but the perpetrator was never definitively identified. The attacks raised significant concerns about bioterrorism and public health preparedness in the United States.