bacillus

noun

Etymology: Learned borrowing from Latin bacillus (“little staff, wand”), diminutive of baculum (“stick, staff, walking stick”).

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

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

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

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

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