A few years ago I had a meeting with a rather successful Danish businessman. As we talked, he had the rather irritating habit of jangling the coins in his pocket. This was annoying in itself, but as I have now discovered, it made the handshake with him one of the more dangerous activities I have undertaken. According to recent research, Danish coins and banknotes are the dirtiest, most bacteria-infested pieces of money you can come across.
As it happens, the Euro, and even Sterling, do relatively well. But the best bet is to go fully cashless and refuse to do business with coins and notes. And avoid meetings with businessmen jangling Danish coins.