bacillus

noun3

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.' — 1895
2. •
   Any bacilliform (rod-shaped) bacterium.
3. •
   (figurative) Something which spreads like bacterial infection.

   • The “bacillus of boom or depression,” he wrote, travels freely “from country to country.” — 1934