noun (n)

• any disease easily transmitted by contact(noun.state)

  Synonym:
  contagious disease
  

  source: wordnet30
• an incident in which an infectious disease is transmitted(noun.event)

  Synonym:
  infection, transmission
  

  source: wordnet30
• the communication of an attitude or emotional state among a number of people(noun.communication)

  Example:
  A contagion of mirth.
  

  source: wordnet30
• The transmission of a disease from one person to another, by direct or indirect contact.(noun)

  source: webster1913