Hi! URI is a bacterial infection, not a viral one, and cannot be transmitted. However, very rarely can a virus jump over, usually with devastating consquences if it does (only episodal evidence).
We therefore recommend to please use commonsense and good hygiene when you have a cold or flu. Don't have long cuddles with your piggies while you are still highly infectious and keep interaction to a minimum during those times, even if you would love a cuddle when you are feeling low! Wash your hands well before you feed, medicate or handle your piggies and refrain from giving kisses (and ideally sneezing and coughing all over your piggies, too).