Plagued Hero - Where to put it

[ese-aSH]

Hi,

I am playing a game as MA T'ien Ch'i and recently a random hero appeared. The hero is appealing (he got several magic paths, including D2, which is cool for t'ien ch'i), but it is said he spreads plague.
My question is : does plague spread only in the province where he stands or does it go further ?

I want to use that guy, I can affort to build a lab just for him, but I surely cant let him contaminate my old mages.

thanks for your answers