noun (plural rickettsiae /-ɪiː/ or rickettsias)
- any of a group of very small bacteria that include the causative agents of typhus and various other febrile diseases in humans. Like viruses, many of them can only grow inside living cells, and they are frequently transmitted by mites, ticks, or lice.
- Genus Rickettsia, order Rickettsiales; Gram-negative rods
modern Latin, named after Howard Taylor Ricketts (1871–1910), American pathologist