Renfield's URI consisted of one sneeze.
Rochester's URI consisted of conjunctivitis with a clear discharge and an extreme degree of sinus congestion. He was nebulized daily for a week, given pediatric decongestant drops, and I still sat up with him several nights in a row convinced that he would die in my arms. He squeaked with every pitiful breath.
Loomis' URI consisted of sneezing, some congestion with clear to gray nasal discharge, and what appeared to be a very sore throat which caused him to stop eating entirely. He was hospitalized twice, once for over a week with a stomach tube, and he very nearly died.
They all came from the same shelter, and were all sick together, but it manifested in totally different ways. Every cat is different.