The Omega Man (Far better than I Am Legend)
Previously filmed as "The Last Man on Earth", I think, some time in the 60s... I have the book but haven't read it yet.
You mention Andromeda Strain - one of the better superbug-threatens-mankind films I thought - an early Michael Crichton. He put out some mixed stuff... Timeline is not among his best, I fear, despite having Anna Friel to look at.
OK, wilfully obscure now - How about La Jetée..?