When Richard Dawkins coined the word meme in his 1976 book The Selfish Gene, he wanted a word like gene that conveyed the way in which ideas and behaviour spread within society by non-genetic means. Since then the word has been picked up to describe a piece of information spread by email or via blogs and social networking sites. A meme can be almost anything - a joke， a video clip， a cartoon， a news story - and can also evolve as it spreads， with users editing the content or adding comments. Common collocates in the Oxford English Corpus are spread， pass， and transmit: as with the Internet sense of VIRAL, meme uses the metaphor of disease and infection.