The common cold is a repetitive, lifelong annoyance. A large number of different viruses that infect the nasal tissues cause the common cold, characterized by a runny nose, nasal stuffiness, sneezing and, occasionally, a scratchy throat and low-grade fever. Among the most frequent of the common cold germs are rhinoviruses, coronaviruses, adenoviruses and parainfluenza viruses.
Rhinoviruses
Rhinoviruses are among the most frequent causes of the common cold. The National Institute of Allergy and Infectious Diseases reports that rhinoviruses cause approximately 30 to 35 percent of head colds in adults. Dr. Stephen Greenburg notes in a review article published in the Archives of Internal Medicine that scientists have identified more than 100 different types of rhinoviruses. The medical reference text "Principles and Practice of Infectious Diseases" explains that rhinoviruses are ideally suited for nasal infection, growing optimally at roughly 91 to 95 degrees F---the internal temperature of the human nose and upper airways. The frequency of rhinovirus-induced colds peaks in the fall and again in late spring. Activity is typically low during the winter months. Rhinovirus infections continue at a low rate throughout the summer. Complications with rhinovirus infections prove uncommon, as the virus is unable to thrive in locations outside of the nose and upper airways.
Coronaviruses
Coronaviruses are another frequent cause of the common cold. According to "Principles and Practice of Infectious Diseases," coronaviruses account for more than 10 percent of all colds. In contrast to rhinovirus-induced colds, coronavirus head colds most commonly occur in the winter and spring months, with low activity in the summer and fall. Coronavirus cold symptoms are indistinguishable from those caused by rhinoviruses. Among people with asthma or chronic obstructive pulmonary disease, coronavirus infections may cause a temporary exacerbation of the underlying illness.
Adenoviruses
The Centers for Disease Control and Prevention reports that adenoviruses cause a range of human respiratory illnesses, including head colds, croup, bronchitis and pneumonia. Some adenovirus types also infect the gastrointestinal system, eyes and urinary bladder. Runny nose, fever and sore throat are common symptoms of adenovirus-related head colds. Infants, young children and those with a weakened immune system may develop a more severe respiratory infection. "Principles and Practice of Infectious Diseases" points out that of the more than 50 known types of adenovirus, types 1, 2 and 5 are most commonly associated with cold-like illnesses.
Parainfluenza Viruses
The Centers for Disease Control and Prevention reports that parainfluenza viruses can cause the common cold or more serious lower respiratory tract infections. Lower respiratory tract infections such as croup and bronchiolitis---inflammation of the small airways---most commonly occur in infants and young children. Older children and adults more commonly present with cold-like symptoms when infected with a parainfluenza virus. Repeat infections with parainfluenza viruses can occur throughout life.
References
- "Principles and Practice of Infectious Diseases, Sixth Edition"; Gerald L. Mandell, M.D., et al., Editors; 2004
- National Institute of Allergy and Infectious Diseases: Common Cold Cause
- Archives of Internal Medicine: Respiratory Consequences of Rhinovirus Infection
- University of South Carolina School of Medicine, Microbiology and Immunology Online: Picornaviruses and Rhinoviruses
- Centers for Disease Control and Prevention: Adenoviruses
