con·ta·gious 
(kən-tājəs)
(kən-tājəs)adj.
1. Of or relating to contagion.
2. Transmissible by direct or indirect contact; communicable: a contagious disease.
3. Capable of transmitting a disease: stayed at home until he was no longer contagious.
4. Spreading or tending to spread from one to another; infectious: a contagious smile.
con·tagious·ly adv.
con·tagious·ness n.