Next time you are walking down the street, looking for a bit of a distraction, try this little experiment. When you see someone coming towards you give them a smile, not in a freaky way but a "gee, what a nice day it is" kind of way.
People's reactions can be quite entertaining. Some will be confused, others will ignore you, but most, without even thinking about it, will simply give you a sheepish smile back. It's like a happiness echo. Perhaps inspite of themselves, your cheeriness triggers a response.
I suspect that, like peacefulness, happiness may be a teeny tiny bit contagious.