I've been informed that it's possible it's a Louisiana (or thereabouts) thing. And it may be the common cold (whatever that means), but the cough lasts multiple weeks, and there's no medicine for it except guaifenesin and dextromethorphan. I've lived in the PNW, i was raised in LA County, CA, and i've spent a decade and a half in the US South.

I bet there's things you've heard of in the south that i've never heard of, too.