Most people have experienced the runny nose, sneezing and congestion symptoms associated with the common cold. More than 200 viruses cause colds, and Americans experience more than 1 billion colds every year, according to MedlinePlus, a website of the National Institutes of Health. The nose of a person who has a cold is full of cold-causing viruses, and when he sneezes or wipes or blows his nose, he can spread the viruses. Others can easily inhale those viruses or can pick them up when they touch a virus-contaminated surface. Some of the most common viruses responsible for causing colds are human parainfluenza viruses, rhinoviruses, coronaviruses and adenoviruses.
Human Parainfluenza Viruses
Human parainfluenza viruses, or HPIVs, can cause a series of repeated infections during the course of a person's life, according to the Centers for Disease Control and Prevention. Two of the four types of HPIV, namely HPIV-1 and HPIV-2, can cause upper respiratory tract infections, including colds. Most people experience an infection with an HPIV as children, and young children incur the highest rates of serious illness due to those viruses. According to the medical textbook "Essentials of Pathophysiology: Concepts of Altered Health States," HPIV infections are the most common cold virus and can be more severe in children under 3 years of age.
Rhinoviruses
The most common cause of colds in those between the ages of 5 and 40, rhinoviruses most often cause those colds during the early spring and late fall, according to "Essentials of Pathophysiology: Concepts of Altered Health States." The National Institutes of Health mentions that rhinoviruses cause between 30 and 35 percent of colds experienced by adults and play a role in approximately 50 percent of asthma attacks. It has proven difficult to develop vaccines against rhinoviruses. Those viruses usually enter the body through the nose, but the eyes and the mouth provide other possible routes of infection.
Coronaviruses
Coronaviruses, which can infect animals as well as people, are another common cause of colds as well as the potentially fatal severe acute respiratory syndrome, or SARS. Coronaviruses cause approximately one-third of colds, mentions Richard Hunt, on the University of South Carolina School of Medicine's Microbiology and Immunology On-Line website. Colds caused by coronaviruses are more common in the winter and spring.
Adenoviruses
Adenoviruses can cause the common cold and other respiratory diseases, including pneumonia and bronchitis, notes the CDC. The viruses can also cause gastroenteritis, bladder infections and conjunctivitis. An illness known as acute respiratory disease, or ARD, may result from infections with adenoviruses. Infections and colds from adenoviruses occur most often during the winter and spring.
References
- MedlinePlus: Common Cold
- "Essentials of Pathophysiology: Concepts of Altered Health States"; Carol Mattson Porth; 2006
- Centers for Disease Control and Prevention: Human Parainfluenza Viruses (Common Cold and Croup)
- University of South Carolina School of Medicine: Microbiology and Immunology On-Line: Rhinoviruses
- University of South Carolina School of Medicine: Microbiology and Immunology On-Line: Coronaviruses, Colds and SARS
