Come to the aid of 10 wounded travelers across the Broken Isles.
After having been bopping along in Legion wondering why I was getting nothing but the same three "Fevered" letters, I saw a comment posted elsewhere that stated you won't get the other quest items to drop if you don't return to the First Aid trainer and learn the other skills. The Fevered notes will drop with nothing more than the basic Legion First Aid (700) and the very first offered skill of treating fevers. The other notes will not drop if you don't have the proper skill to cure them learned first.
Get yourself back to the trainer! :)