What Is a Common Cold?
Sneezing, scratchy throat, runny nose -- everyone knows the first miserable signs of a common cold. But what is a common cold really? What causes you to catch colds frequently while your best friend stays well? And more importantly, how can you prevent getting a cold this season? Here are some common cold basics to help you protect yourself and your family from getting sick.
The common cold is a group of symptoms in the upper respiratory tract caused by a large number of different viruses. Although more than 200 viruses can cause the common cold, the perpetrator is usually the rhinovirus, which is to blame for causing 10% to 40% of colds. Also, the coronaviruses cause about 20% of colds and the respiratory syncytial virus (RSV) causes 10% of colds.
Although the common cold is usually mild, it is a leading cause of doctor visits and missed days from school and work. According to the CDC, 22 million school days are lost annually in the U.S. because of the common cold. Some estimates state that Americans suffer 1 billion colds annually.
For more detail, see WebMD's article on Common Cold Causes.
More than 200 different viruses are known to cause the common cold -- and the miserable symptoms that come with it.
The most common cold viruses include:
• Rhinoviruses -- causing 10% to 40% of colds
• Coronaviruses -- causing 20% of colds
• Respiratory syncytial virus (RSV) -- responsible for 10% of colds
Rhinoviruses and the Common Cold
Rhinoviruses, the worst offenders, are most active in early fall, spring, and summer. More than 110 distinct rhinovirus types have been identified. Most rhinoviruses seldom produce serious illnesses. However, other cold viruses, such as parainfluenza and RSV, can lead to severe lower respiratory infections, such as pneumonia, in young children
Coronaviruses and the Common Cold
Scientists think coronaviruses cause a large percentage of adult colds. These cold viruses are most active in the winter and early spring. Of the more than 30 kinds of coronaviruses, three or four infect humans.
Other Causes of the Common Cold
About 10% to 15% of adult colds are caused by viruses also responsible for other, more severe respiratory illnesses.
The causes of 20%-30% of adult colds, presumed to be viral, remain unidentified. The same viruses that produce colds in adults appear to cause colds in children. The relative importance of various viruses in children's colds, however, is unclear because it's difficult to isolate the precise cause of symptoms in studies of children with colds.
There is no evidence that you can get a cold from exposure to cold weather or from getting chilled or overheated.
Stress, Allergies, and the Common Cold
There is also no evidence that your chances of getting a cold are related to factors such as exercise, diet, or enlarged tonsils or adenoids. On the other hand, research suggests that psychological stress and allergic diseases affecting your nose or throat may have an impact on your chances of getting infected by cold viruses.
How a Common Cold Starts
With a common cold, you can catch it from another person who is infected with the virus. This usually happens by touching a surface contaminated with cold germs -- a computer keyboard, doorknob, or eating utensil, for example -- and then touching your nose or mouth. You can also catch a cold by encountering secretions someone with a cold has sneezed into the air.
A cold begins when a cold virus attaches to the lining of your nose or throat. Your immune system sends white blood cells out to attack this germ. Unless you've encountered that exact strain of the virus before, the initial attack fails and your body sends in reinforcements. Your nose and throat get inflamed and produce a lot of mucus. With so much of your body's energy directed at fighting the cold virus, you're left feeling tired and miserable.
While getting chilled or wet is not a cause of common colds, there are factors that make you more susceptible to catching a cold virus. For example, you are more likely to catch a common cold if you are excessively fatigued, have emotional distress, or have allergies with nose and throat symptoms.
Common Cold Symptoms
With the common cold, you may have cold symptoms such as an itching or sore throat with sneezing, nasal congestion, watery eyes, and mucus drainage. More severe symptoms, such as high fever or muscle aches, may indicate you have a flu rather than a cold.
For more detail, see WebMD's article on Common Cold Symptoms: What You Might Feel.