contagion

plural contagions

1. countableuncountableA disease spread by contact.

   He is plague-stricken, surrounded by a poisonous atmosphere, infected by a contagion of death; his very touch may blight the earth.

   1918, James George Frazer, Folk-Lore In The Old Testament, volume 1, page 80

2. countableuncountableThe spread or transmission of such a disease.

   Synonyms: infection

3. The spread of anything likened to a contagious disease.
   1. broadlycountablefigurativelyuncountableThe passing on of manners or behaviour through a closed community or household.

      1 more example

      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.

      1838 (date written), L[etitia] E[lizabeth] L[andon], chapter XIX, in Lady Anne Granard; or, Keeping up Appearances. […], volume I, London: Henry Colburn, […], published 1842, →OCLC, page 242

   2. broadlycountablefigurativelyuncountablebusinessThe spread of (initially small) shocks, which initially affect only a few financial institutions or a particular region of an economy, to other financial sectors and other countries whose economies were previously healthy.

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

      2011, George Soros, Project Syndicate, Germany Must Defend the Euro

4. countableuncountablebusinessA recession or crisis developed in such manner.