contagion

noun

1. (countable, uncountable)A disease spread by contact.
2. (countable, uncountable)The spread or transmission of such a disease.
3. (broadly, countable, figuratively, uncountable)The spread of anything likened to a contagious disease.

   “It is true, they were a good-natured and respectable set of servants, who had lived so long in their places that they might be said, by a happy contagion, to have caught kindly feelings from their superiors, and, having assisted in saving the lives of the young ladies, gave them an interest in their pleasures, and a real delight in seeing those fair young faces lighted up with joy.”

4. (broadly, countable, figuratively, uncountable)The spread of anything likened to a contagious disease.

   “And it was German procrastination that aggravated the Greek crisis and caused the contagion that turned it into an existential crisis for Europe.”

5. (countable, uncountable)A recession or crisis developed in such manner.