I read about it in the book Scourge: The Once and Future Threat of Smallpox. The book was released September 2001, and it had incredible timing. It was just before the terrorist attacks on September 11 and a month before the anthrax attacks on the US Senate via the US mail.
Another good book on the topic of biological warfare is The Demon in the Freezer: A True Story.
Thanks for the reply.