An upper respiratory infection (URI), also known as the common cold, is one of the most common illnesses, leading to more health care provider visits and absences from school and work than any other illness every year.It is estimated that during a 1-year period, people in the U.S. will suffer 1 billion colds.n fact, over 200 different varieties of viruses can cause the symptoms of a cold. The most common viruses that cause colds are called rhinoviruses. Other virus types include coronavirus, parainfluenza, adenovirus, enterovirus, and respiratory syncytial virus.