I looked all over the place for an infected creature right after the patch that was supposed to increase the odds.
Found none.
Then I got the idea to carry blackrock around with me.
I found 5 creatures in about an hour. Or rather I infected them. They changed right on my screen and attacked me.
Next day I got 4 more.
Although there was nothing special about them except creature types that usually dont carry gold had some.
no special items yet.
I have never cast armegeddon as I dont have enough magery.