Contagious (adjective)

1. Capable of being passed on from one person or organism to another by close proximity or contact.
2. Easily spread by contact.

Origin:

Late middle english: from latin contagiosus, from contagio "contact, contagion", from con- "with" + tangere "to touch".

Examples:

1. The flu is contagious and can be spread easily from person to person.
2. The disease was highly contagious and quickly spread through the population.
3. She found out that the rash was contagious and took precautions to avoid spreading it.
4. The excitement was contagious and soon everyone was cheering.
5. The happiness was contagious and it spread throughout the room.