Bad Breath, something that we catch?

by my boy's mom
(Dallas, TX)

I have noticed that somehow my son had this on-set of bad breat when he was 11 years old. Just like that he had bad breath and has it ever since.
Is it some kind of virus that we don't know about?
Is it some kind of vitamin/mineral deficiency?
I read that people that don't have bad breath have good bacteria in their mouth and people with bad breath don't. Why?