Rat-Borne Illnesses Rats carry various diseases as a result of their filthy lifestyles. Some of the most commonly transmitted maladies include leptospirosis, plague, salmonellosis, and tularemia. One particularly dangerous disease is rat-bite fever, which can be contracted via the bites of infected rats or the consumption of contaminated food and water. Some symptoms include vomiting, headaches, muscle and joint pain, swollen lymph nodes, and rashes. It is important to note that rat-bite fever cannot be transmitted from person to person. Symptoms and Treatment Symptoms typically start occurring within one week of exposure after the actual bite or scratch has healed. Those infected with, or those who suspect they may have, rat-bite fever should seek immediate medical attention. Leaving rat-bite fever untreated can be fatal, as the illness leads to other health problems in the heart, brain, and lungs, including meningitis, and pneumonia.