"contagion" in the noun sense
1. contagious disease, contagion
any disease easily transmitted by contact
2. infection, contagion, transmission
an incident in which an infectious disease is transmitted
3. contagion, infection
the communication of an attitude or emotional state among a number of people
"a contagion of mirth"
"the infection of his enthusiasm for poetry"
Source: WordNet® (An amazing lexical database of English)
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