Now, the question is, did Atta lick the envelope flaps or did someone else?
CDC could check death records for the period September 8, 2001 to the present and find some Middle-Easterner, possibly a child, who died of symptoms suspiciously like those of anthrax.
Whoa. Good thinking. Check the envelope flap for saliva and DNA (unless a sponge was used to dampen the glue or the envelopes were self-sealing). They could also look for some Middle-Easterner, who was murdered (before developing anthrax.) or was given Cipro. Come to think of it, I wonder if Kathy Nguyen was asked by anyone to lick envelopes.
The early report on the envelopes (within days of the attacks) was that the flaps were not sealed, rather they were tucked in "loose". This is why the powder could be leaking on equipment during handling and contaminating adjacent envelopes (not always to a lethal level, but to a measurable degree).