CDC diagram of mail flow during the 2001 anthrax attacks
Centers for Disease Control and Prevention (original), <a href="//commons.wikimedia.org/wiki/User:Augurar" title="User:Augurar">Augurar</a> (SVG version)
2002-03-26
<a rel="nofollow" class="external free" href="ftp://ftp.cdc.gov/pub/infectious_diseases/iceid/2002/pdf/holtz.pdf">ftp://ftp.cdc.gov/pub/infectious_diseases/iceid/2002/pdf/holtz.pdf</a>