bacillus

plural bacilli

1. Any of various rod-shaped, spore-forming aerobic bacteria in the genus Bacillus, some of which cause disease.

   "You will conceive a bunch of grapes," said he, "which are covered by some infinitesimal but noxious bacillus.

   1913, Arthur Conan Doyle, “(please specify the page)”, in The Poison Belt […], London; New York, N.Y.: Hodder and Stoughton, →OCLC

   1 more example

   'This again,' said the Bacteriologist, slipping a glass slide under the microscope, 'is a preparation of the celebrated Bacillus of cholera - the cholera germ.'

   1895, H. G. Wells, The Stolen Bacillus

2. Any bacilliform (rod-shaped) bacterium.
3. broadlyfigurativelySomething which spreads like bacterial infection.

   The “bacillus of boom or depression,” he wrote, travels freely “from country to country.”

   1934 [2018], Gottfried Haberler quoted in Quinn Slobodian, Globalists, 71