There is always news stories like this going round, however you actually have to look at the stats.
It only looked at 45 used bank notes, granted the percentages would be still be quite high, but it would have a far greater impact if it had taken samples say from 1000 bank notes, again the area where they took the sample would have to be considered too, for example if the notes were taken from an inner city bank, then the likelihood of there being traces of charlie would be higher.
There was a recent study that something like 90% of banknotes had herpes on them or something like that, I will try and track down the story later.