The causative agent of a communicable disease; contagion.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "contagium" in a sentence
"It is doubtful whether it can be conveyed from one person to another; at least nothing is known concerning the "contagium," or germ of conveyance of infection, -- according to the differential diagnosis of Dr.G. Kuhnemann, whose work on the subject is held to be authoritative."
"Tui precatus munere nostrum reatum dilue, arcens mali contagium, vitæ repellens tædium."
"The breath and emanations from the skin transmit the _contagium_ from the appearance of the first symptom to the disappearance of the eruption."