Viral phenomena are objects or patterns that are able to replicate themselves or convert other objects into copies of themselves when these objects are exposed to them. Analogous to the way in which viruses propagate, the term viral pertains to a video, image, or written content spreading to numerous online users within a short time period. This concept has become a common way to describe how thoughts, information, and trends move into and through a human population.

The popularity of viral media has been fueled by the rapid rise of social network sites, wherein audiences—who are metaphorically described as experiencing "infection" and "contamination"—play as passive carriers rather than an active role to 'spread' content, making such content "go viral". The term viral media differs from spreadable media as the latter refers to the potential of content to become viral. Memes are one known example of informational viral patterns.

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