Can someone help me remember the name of this 70's sci-fi/horror film?

I’m not even sure when it was made, just that I last remember seeing it on cable in the late 70’s or very early 80’s.
It was a very atmospheric thriller that told the story of everyone in a small town suddenly dying. The town’s only survivors were an infant who was at home, and the town drunk. The movie then followed scientists as they attempted to find out what killed the town’s citizens as some of the scientists began to die off too. (I think)

I know I didn’t dream this. Does anyone else remember this movie, and most importantly the title of it?

Thank you.

The Andromeda Strain

That’s what I immediately thought of.

Reading the synopsis at the IMDB, I think that’s it!
Thank you for the quick responses.

Excellent movie and the book is even better.