What movie/series is this?

Long time ago when I saw I think it was a movie or series I cant remember.

But the premis was some kind of alien that took control of humans (they become infected)
The alien infected the humans by crawling out of a infected mouth into another ones mouth.

I remember one scene were they were inspecting dead body ad a mortary where she opend her eyes and the (alien crawled out of her mouth slowly to the guy who was inspecting her.

Anybody recognize this and can tell me wich movie series this is? Or maybe i just imaged it?