I remember watching a sci-fi film in the early to mid 70s where the beginning saw a man in a protective suit wandering round a deserted town covered in a red light. Vaguely think there was some sort of virus outbreak but not much else. Trying to think of the film name is driving mad!! Checked on imdb, wiki but no joy as yet. Help me (insert name) you're my only hope!

It has been many years since I have seen this film but I am pretty sure you are thinking of The Andromeda Strain.

The Andromeda Strain (1971) (http://www.imdb.com/title/tt0066769/)