The most prevalent of all human illnesses, the common cold, is a minor infection of the upper respiratory tract. It mainly involves the nose and throat but can extend to the sinuses, ears, and bronchial tubes. As a general rule, cold symptoms are milder than flu symptoms and most people recover in seven to ten days. Some signs of the common cold are:
- low grade fever
- sore throat
- coughing and/or sneezing
- nasal congestion or runny nose
- slight muscle aches
- mild headaches
- watery eyes
Cold symptoms generally emerge between one and three days after a cold virus enters the body and resolve in a week — with or without medication. One cold in four lasts up to 14 days; this most often occurs in children, the elderly, and people who are in poor health. Smokers often have more severe, extended cold symptoms than nonsmokers.
Fewer than 5 percent of colds lead to such complications as bronchitis, middle-ear infection, or sinusitis accompanied by a prolonged cough, but between 5 and 15 percent of children who have colds develop acute ear infection when bacteria or viruses infiltrate the space behind the eardrum. A cold can produce wheezing, even in children who do not have asthma, and symptoms of asthma, bronchitis, and emphysema can be exacerbated for many weeks. Symptoms that persist for more than two weeks or that recur might be more allergy than infection related.
Post-infectious cough, which usually produces phlegm, may disrupt sleep and persist for weeks or months following a cold. This complication has been associated with asthma-like symptoms and can be treated with asthma medications prescribed by a physician. Medical attention is indicated if symptoms progress to:
- ear pain
- high fever
- a cough that worsens as other symptoms abate
- a flare-up of asthma or of another chronic lung problem
- significantly swollen glands
- strep throat
Beginning in late August or early September, the incidence of infection rises gradually for a few weeks and remains elevated until declining in March or April. Seasonal variations in susceptibility may be related to cold weather or to months when school is in session―times when people spend more hours indoors and chances of interpersonal transmission are enhanced. Changes in relative humidity may also have an effect. Cold temperatures dry the lining of nasal passages and increase vulnerability to infection by common cold-causing viruses that thrive in such weather.
Over the course of a lifetime, a person has been estimated to spend the equivalent of five years suffering from the common cold. One-fifth of that time, cold symptoms are severe enough to require bed rest. Women get more colds than men―especially women between 20 and 30 years of age―and adults over 60 years of age get less than one cold a year on average.
Learn more about the common cold and influenza through our homestudy courses.