Viral phenomena are objects or patterns able to replicate themselves or convert other objects into copies of themselves when these objects are exposed to them.
The concept of something, other than a biological virus, being viral came into vogue just after the Internet became widely popular in the mid to late 1990s. An object, even a non-material object, is considered to be viral when it has the ability to spread copies of itself or change other similar objects to become more like itself when those objects are simply exposed to the viral object. This has become a common way to describe how thoughts, information and trends move into and through a human population. Memes are possibly the best example of viral patterns. The 1992 novel Snow Crash explores the implications of an ancient memetic meta-virus and its modern day computer virus equivalent, "We are all susceptible to the pull of viral ideas. Like mass hysteria. Or a tune that gets into your head that you keep on humming all day until you spread it to someone else. Jokes. Urban legends. Crackpot religions. Marxism. No matter how smart we get, there is always this deep irrational part that makes us potential hosts for self-replicating information." (see Crash" target="_blank">wikiquote)
Some consider humanity to be a form of viral phenomenon as they have the ability to reproduce to the point where they are nearly omnipresent, and yet continue to replicate at the expense of another system. As a virus replicates by using host cell(s), humanity has replicated at the expense of the _Earth and the environment.
Examples of viral phenomena in addition to memes are:
