Rhinoviruses

These viruses are responsible for 25% of the colds seen in the U.S. These viruses are polio and cold causing viruses are changeable to pH of 3 therefore they are not present in the gastrointestinal tract as one would see the poliovirus. These viruses also grow optimally at 33° C which is the temperature of the nasal mucosa of humans.

These viruses are enveloped RNA viruses. More than 20 strains of coronaviruses have been obtained from humans. In adults coronaviruses can cause from 10 to 24% of common colds.

Both these viruses are picornaviruses which are placed in the enterovirus category due to their residence in the intestines. Coxsackieviruses are grouped into groups A and B. Each group consists of several serotypes. Echoviruses are not grouped but several types exist. Usually these viruses cause aseptic meningitis and pleurodynia (pain in the intercostal muscles due to irritation of pleural surfaces) but occasionally they have been found to cause the common cold.

This group of viruses contains Influenza viruses, Parainfluenza viruses, and Respiratory Syncytial virus; all of which can cause the common cold. Influenza viruses (types A, B, and C) typically cause influenza, which we will discuss later, however it can also cause the common cold. In adults the four types of parainfluenza viruses can cause the common cold, however, in children these viruses can cause severe disease including croup, bronchitis, and pneumonia. Respiratory syncytial virus causes the common cold in adults. In children it is associated with severe lower respiratory tract infections.

Only a few of the 34 types of adenoviruses cause the common cold. These infections are particularly a problem in military recruits.

This organism is not a virus but rather a cell-wall deficient bacterium. This organism can cause respiratory infections that range from the common cold to bronchopneumonia.