Smiling is infectious, u catch it like flu

Smiling is infectious,
you catch it like the flu.
when someone smiled at me today,
I started smiling too.
I passed around the corner,
and someone saw my grin.
when he smiled I realized.
I’d passed it on to him!
I thought about that smile,
then I realized it’s worth.
a single smile just like mine,
could travel round the Earth