A rat bite will typically only happen when the rodent feels cornered or in danger. This can occur when someone attempts to cage the rat or mouse, or if they come across one in the wild. Rat bites can be either shallow or deep, and can draw blood. When rodents bite, there are a few concerns—namely, the risk of contracting a disease. This is because the saliva of some types of rats carries hazardous diseases. While rare, deer mouse bite victims can contract Hantavirus, and rat bite victims can contract rat-bite fever.