As a consequence of these unfortunate events associated with the use of primary monkey kidney cells in the early 60s and the emergence of approximately 20 or 30 viruses... different viruses found in the cells and the necessity for tests to exclude them, and all of the other efforts in this regard, the... my proposal of using... or my normal human cell strains for this purpose, in particular WI-26, which became widely circulated for experiments that addressed this problem, the... there occurred another even that was even of greater consequence.

And that was that in efforts to explore the use of other monkey species for vaccine development and manufacture, and hopefully to find a species that lacked these dangerous viruses, Maurice Hilleman at Merck and a man by the name of Benjamin Sweet did experiments, I believe it was with the green monkey, cercopithecus aethiops, which revealed something very interesting.

I won't go through the technology in which this was discovered; that's rather detailed and irrelevant other than the conclusion. And the conclusion was that green monkey cells yielded a result implying that a new virus was present in the cells from... from rhesus and cynomolgus monkeys that had very strange properties. And they called this virus – I believe they were the ones who named it – SV40.  All of the viruses found in money kidney were given the name SV, standing for Simian Virus, and they were numbered. This one then received the number 40. And about the same time, events were occurring that would link with this observation at the National Institutes of Health.