More anthrax letters and cases in the United States

A fourth letter containing anthrax spores was discovered on 16 November in the United States (US) by investigators from the Federal Bureau of Investigation (FBI) and the US Postal Service (1). They had been sifting through unopened US government mail that was quarantined after a previous anthrax laced letter was discovered on 15 October in the office of Senator Tom Daschle. In order to preserve forensic evidence, the letter has not yet been opened, but preliminary field tests have been positive for B. anthracis, and the envelope is believed to contain billions of spores.