Take the concept of apocalypse zombie.
Now take the parasite, yk, the one that transform the humans. Make it that it changes they appearance but keep the urge of infecting others.
The human "losses" (kinda) their memories but is still as (maybe more) intelligent than before.
Now because the idea was from a furry, the changes in the human's appearance are anthropomorphic. The changes impact his sense too, they gain the pros and cons of the animal.
And yeah infection is not by bite but by prolonged contact.
And that's pretty much it.
Those aren't humans anymore, like in the zombie apocalypse. And they behavior can be solo or grouped, depends again on the anthro characteristics.