I am trying to determine when the phrase "going viral" was first used. Similarly, when did the phrases "viral video" and "viral marketing" get their start? I have looked online at various sites, but none really address this question (other than saying "recently").
The Oxford English Dictionary's earliest citation for the use of viral in the sense of ‘involving the rapid spread of information’ is dated 1989. The earliest citation actually including the verb go is as late as 2004:
I found no earlier example than the one in Callithumpian's comment from July 31, 2000 by Seth Godin for Fast Company:
"go viral" OR "went viral" OR "gone viral" OR "going viral"
The earliest I found is from 21 March 2003 in an article by MediaWeek titled:
In 2002, search engine Lycos had set up a Viral Chart for people to upload the viral attachments that people spread via email. When promoting the chart in May 2002, they referred to viral videos:
Here's an archive of the Lycos Viral Chart.
I found nothing earlier than the 1989 Barrie noted from the OED, in PC User: