The common cold is actually a description of a broad range of viral upper respiratory infections rather than a single illness. It is generally thought by virologists that more than 200 different types of viruses can infect the upper respiratory tract and cause the symptoms of a cold. Though the exact proportion is uncertain, approximately one-third or more of colds are caused by rhinoviruses.
Rhinovirus Infection
Rhinoviruses belong to the family Picornaviridae. Roughly 100 serotypes of rhinovirus are known to exist. These serotypes have been traditionally divided into two genetic subtypes (HRV-A and HRV-B), but a third novel subtype (HRV-C) was recently discovered and has been associated with more severe illness. Some studies have found a significant association between the seemingly harmless and easily cleared upper respiratory rhinovirus infection and asthma and wheezing in children, as well as sinusitis and chronic obstructive pulmonary disease in adults.
The wide range of viral serotypes makes vaccination against this virus difficult. The acute respiratory infection it causes, known as a cold, is usually self-limiting, but has a large economic impact, resulting in lost productivity, diminished work force, and strained health care system, particularly in pediatrics. The majority of infections occur in children and adolescents under the age of 17 years, and medical treatment is sought for most children under the age of five years.
Common Cold Symptoms
The symptoms of the acute upper respiratory infection caused by rhinoviruses include coughing, sneezing, sore throat, stuffy and runny nose, and itchy eyes. The symptoms are all the result of the virus invading the cells of the upper respiratory system or the immune response to its presence. The first response to the presence of the pathogen is the secretion of mucus in the nose and respiratory tract (sneezing, stuffy and runny nose). The mucus is an attempt by the body to prevent the virus from entering the cells of the mucus membranes. The immune response then causes slight inflammation, resulting in the itchy and irritated membranes (sore throat, itchy eyes, coughing).
Children often develop a fever with the infection, but it is not common in adults. Headaches, muscle aches, and fatigue may also develop as the body defends itself and uses up resources to rid itself of the pathogen. Rhinoviruses have a short incubation period of roughly eight to 10 hours but may linger, according to the Centers for Disease Control and Prevention (CDC), for up to two weeks.
Treating Colds and Rhinovirus Infection
Most viral infections are best treated with rest and fluids because there is no treatment except to let it run its course. Over-the-counter pain reliever, decongestants, and anti-histamines can help treat the symptoms and make the illness more comfortable. In the case of secondary bacterial infections, a common complication, antibiotics may be prescribed. The CDC recommends that children with symptoms lasting more than 10 days who are unresponsive to over-the-counter medications or with fevers over 100.4 degrees Fahrenheit seek medical attention.
References:
Briese et al. Global distribution of novel rhinovirus genotype. Emerging Infectious Diseases. 2008; 14(6), 944-947.
Hunt. Virology Ch 10, part 2: Rhinoviruses. University of South Carolina School of Medicine, Microbiology and Immunology Online. Accessed Dec. 27, 2009.
Linsuwanon et al. Recurrent human rhinovirus infections in infants with refractory wheezing [Letter]. Emerging Infectious Diseases. 2009; 15(6). Available from the CDC website.
Rollinger and Schmidtke. The human rhinovirus: Human-pathological impact, mechanisms ofantirhinoviral agents, and strategies for their discovery. Medicinal Research Reviews. 2009; doi 10.1002/med.20176
Alicia Mae Prater - Alicia received her doctorate in Experimental Pathology in 2007. She has been a freelance writer and scientific editor since 2008.
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