The human mouth is chocked full of germs and bacteria. You can imagine how much bacteria would be on your toothbrush. The biggest problem with a toothbrush packed with bacteria is that if you have the flu or a cold, you can reinfect yourself by using the toothbrush.
A new USB gadget called the UVmini has surfaced that uses UV light to kill germs and sanitize your toothbrush. UV light is well known for its ability to kill germs, so the gadget is based on reliable tech.
The strange part for me is that the UVmini is something that you would use in the bathroom, yet it is powered by a USB port. I guess you could use your Apple Ac adapter to plug the UVmini in your bathroom outlet. One version has a rechargeable battery good for an hour of sanitizing per charge. Pricing and availability are unknown.