Copper and subsequent copper alloys including brass and bronze, have proven antimicrobial properties which destroy both viruses and bacteria within 2 hours of exposure. According to the Copper Development Association, when viruses and bacteria meet with copper they are flooded with copper ions which are recognized as essential nutrients and penetrate the cell. Once the ion has entered the cell it begins to prevent cell respiration, punches holes in the cell membrane, and destroys the DNA and RNA inside. Interestingly this destruction of the genetic material means that no mutation can occur and the microbe is unable to develop a resistance to the copper ions.
* Source: U.S. EPA, CDA