AP Style - Sept. 11 and 'outbreak' entries
A couple more miscellaneous updates to AP style:
For disease references, reserve for larger numbers of an illness, not a few cases.
Sept. 11 (update)
The term for describing the terrorist attacks in the United States on Sept. 11, 2001. Use 2001 if needed for clarity. Also acceptable is 9/11. See 9/11 entry.
(Note that under the USC j-school style guide, we spell it out -- September 11. We have decided it is an event as momentous in this nation's history as July Fourth, which is spelled out.)