Answer
When an healthy rat is exposed to pneumonia, it can develop Pneumonia virus of mice( PVM)
Step-by-step explanation
The Pneumonia virus of mice (PVC) is a ssRNA virus from the family of Paramyxoviridae which can develop in mice and rats to affect their respiratory tracts. This virus could be transmitted through a contact exposure to the respiratory track or via an aerosol. The infection is fatal and can be eradicated by culling of the colony and getting a clean replacement stock.