Fluffy, a 12-year-old unvaccinated Persian cat, comes into your clinic. She has always been an indoor cat with no exposure to the outside (including the patio). Her owner found a kitten 10 to 14 days prior with a mild cold wandering around outside her house and brought it inside the house. She brought it to the Humane Society the next day. Fluffy liked the kitten and sniffed it a few times. Fluffy is now running a fever (104.5), is sneezing, has mild ocular discharge, and is not eating. Which of the following is NOT a possible cause of Fluffy's problem