The Man Who Bit a Fell-Beast

[Inziladun]

Originally Posted by Boromir88

Sauron didn't want to be outed at this early stage in his designs yet. Appendix B notes that in circa 1100 the Istari and Eldar believed the power that came to Dol Guldur was a Nazgul. TA 1636 the plague spreads through Gondor and if Sauron did engineer it, he still would be laying low and not wanted his enemies to know he's returned. Targeting Gondor first may have revealed Sauron was behind it before he wanted to be outed.

Somewhere in the books, there's a reference to Mordor originally being merely Sauron's westernmost stronghold, outside his original realms "in the East".
If that's the case, he would have returned to that area in exile, as it were. Therefore, releasing the plague from the direction of Rhûn was unavoidable. Gondor at that point believed Sauron had perished at the end of the Second Age, at any rate.
Obviously, he would have known that the Men under his sway were susceptible also, but I doubt he would have been much troubled by that. He knew open war with the West was a long time away, and he had plenty of time to rebuild an army.