The common cold is a self-limited contagious
disease that can be caused by a number of different types of viruses. The common cold is medically referred to as a viral upper respiratory tract infection
Other commonly implicated viruses include coronavirus, adenovirus, respiratory syncytial virus, and parainfluenza virus
Because so many different viruses can cause the common cold, and because new cold viruses constantly develop, the body never builds up resistance against all of them.