Scientists say the power of copper to fight germs lies in the fact that copper ions separate on contact with bacteria and cause irreversible damage to the bacteria's cells.
Bacteria have tiny channels in their walls which operate like the valve on a pressure cooker - they open to release material when the pressure in a bacterial cell gets too great. If the channel didn't open to relieve pressure the bacteria would explode and die, so this is a target for drug development.
The death toll in China's outbreak of hand-foot-mouth disease has risen to 42 children, with the capital Beijing reporting its first case on Wednesday.