Cold is probably the most common illness known? But although the common cold is usually mild, with symptoms lasting one to two weeks, it is leading cause of doctor visits and missed days from school and work.

Children have about six to 10 colds a year. One important reason why colds are so common in children is that they are often in close contact with each other in daycare centers and schools.

In families with children in school, the number of colds per child can be as high as 12 a year. Adult average varies widely. Women, especially those aged 20 to 30 years, are more prone to colds than men, possibly because of their closer contact with children. On average, people older than 60 have fewer than one cold a year.

Causes:

The Viruses

More than 200 different viruses are known to cause the symptoms of the common cold. Some, like the rhinoviruses, seldom produce serious illness. Others, such as Para influenza and respiratory syncytial virus, produce mild infections in adults but can precipitate severe lower respiratory infections in young children.

Rhinoviruses (from the Greek word rhin, meaning “nose” cause an estimated 30 to 35 percent of all adults colds. More than 110 distinct rhinovirus type have been identified. These agents grow best at temperatures of about 91F, the usual temperature inside the human nose.

Scientist think coronaviruses cause a large percentage of all adults’ colds. Of the more than 30 kinds of coronavirus, three or for infect humans. The importance of coronaviruses as a cause of colds is hard to asses because, unlike rhinoviruses, they are difficult to grow in the laboratory.

Approximately 10 to 15 percent of adult colds are caused by viruses also responsible for other, more severe illnesses: adenoviruses, coxsackieviruses, echoviruses, orthomyxoviruses including influenza A and B viruses, which cause flu ), paramyxoviruses (including several parainfluenza viruses), respiratory syncytial virus and enteroviruses.

The causes of 30 to percent of adult colds, presumed to be viral, remain unidentified. The same viruses that produce colds in adults appear to also cause colds in children. The relative importance of various viruses in pediatric colds, however, is unclear because it is difficult to isolate the precise cause of symptoms in studies of children with colds.