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. They get their name from the way that viruses propagate. 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-known example of informational 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. No matter how smart we get, there is always this deep irrational part that makes us potential hosts for self-replicating information. (see wikiquote)||”|
The spread of viral phenomena are also regarded as part of the cultural politics of network culture or the virality of the age of networks Various authors have pointed to the intensification in connectivity brought about by network technologies as a possible trigger for increased chances of infection from wide-ranging social, cultural, political, and economic contagions. For example, the social scientist Jan van Dijk warns of new vulnerabilities that arise when network society encounters “too much connectivity.” The proliferation of global transport networks makes this model of society susceptible to the spreading of biological diseases. Digital networks become volatile under the destructive potential of computer viruses and worms. Enhanced by the rapidity and extensity of technological networks, the spread of social conformity, political rumor, fads, fashions, gossip, and hype threatens to destabilize established political order.
On the Left, in their book Empire, Michael Hardt and Antonio Negri have argued that the age of globalization is synonymous with the age of contagion. This is an age in which increased contact with the "Other" has rekindled anxieties concerning the spreading of disease and corruption since permeable boundaries of the nation-state can no longer function as a colonial hygiene shield. The spontaneity of contagious overspills thus has the potential to initiate a revolutionary renewal of global democracy. On the Right, the International Monetary Fund, and various leaders of the capitalist world order have pointed to the threat posed to the stability of the current neoliberal political–economic system by the capricious spreading of financial crises from nation to nation. Correlations have been made, for example, between the interlocking of global stock markets, the chaos of financial contagion, and the so-called Islamic threat to justify the ongoing War on Terror (Tony Blair's speech on the eve of the invasion of Iraq, for example).
Examples of viral phenomena in addition to memes are:
- Virality relating to network culture 
- Viral marketing
- Viral video
- Chain letters
- Viral email
- Viral licenses (such as the GNU General Public License)
- Clothing fashion trends