Have you ever known someone who is so full of energy, enthusiastic and always smiling and happy?
We have a great English idiom called 'Full of Beans' to show that someone can not sit down and has to be active. They will also be very happy and full of energy and very enthusiastic to do any activity!
If you know someone like this, you can say to them:
You are so full of beans, your enthusiasm is so infectious.
Yes, I know infectious means illness, right? Well infectious can be used positively too to show that someones energy and great feeling can be past onto other people.
Very positive idiom, right? Try it out and see how it goes!