When I was young, perhaps around early, or mid, or maybe even late 90s, I watched around the first 30 minutes of what I remember was a low budget American sci-fi horror flick. It was broadcast on our local TV in Serbia, so it could be from the early 90s but also late 80s as well.
I don't remember much except that there was this weird (alien? virus? parasite?) life form that would somehow end up inside living humans, growing until it made them really sick. It obviously involved some scientists researching the phenomenon. I think it was happening in a regular US city on planet Earth, and I remember this gross scene of the life form, now already kinda big, maybe like 10 inches long, looking like a big whitish caterpillar of sorts, leaving a woman's body through her mouth.
Before it finally went out and ended in the scientist's dish, you could see it poking through the neck from within, looking for the exit, gaaaa super gross! Which is why we changed the channel and I haven't seen more of it.