Noun

(en noun)

(pathology, immunology) Any organism or substance, especially a microorganism, capable of causing disease, such as bacteria, viruses, protozoa or fungi. Microorganisms are not considered to be pathogenic until they have reached a population size that is large enough to cause disease.

*{{quote-magazine, date=2013-01

, author=Katie L. Burke , title=Ecological Dependency , volume=101, issue=1, page=64 , magazine= citation , passage=In his first book since the 2008 essay collection Natural Acts: A Sidelong View of Science and Nature , David Quammen looks at the natural world from yet another angle: the search for the next human pandemic, what epidemiologists call “the next big one.” His quest leads him around the world to study a variety of suspect zoonoses—animal-hosted pathogens that infect humans.}}

Noun

(en noun)

A disease spread by contact

The spread or transmission of such a disease

The spread of anything harmful, as if it were such a disease

(finance) A situation in which small shocks, which initially affect only a few financial institutions or a particular region of an economy, spread to the rest of financial sectors and other countries whose economies were previously healthy.

* 2011 , , Project Syndicate, Germany Must Defend the Euro :

And it was German procrastination that aggravated the Greek crisis and caused the contagion that turned it into an existential crisis for Europe.

(finance) A resulting recession or crisis developed in such manner.