Since the terrorist attacks of September 11, letters containing anthrax spores have appeared in the mailrooms of media organisations and government offices across the US and around the world, rattling nerves and heightening Americans' fears of a large-scale bio-terror attack.

Traces of the powdery substance have been found in postal offices in Florida, New Jersey and New York City, high-profile government offices, and in off-site areas where mail addressed to the White House, the Supreme Court and the US Senate is handled. By the end of November, 11 people had been diagnosed with inhalation anthrax, the more deadly form of the disease. Five have died. Seven people have been diagnosed with cutaneous or skin anthrax. .

Before October 5, when Robert Stevens, a photographer for the Sun tabloid newspaper died of inhalation anthrax, pulmonary anthrax had not been reported in the US since the 1970s.