Common Cold

Colds are minor infections of the upper respiratory tract, including the nose and throat. They are common illnesses in the United States, with some authorities reporting an average of 1 billion cases of the common cold every year.

Many different types of viruses cause colds. Typically, viruses are relatively harmless and live in the body for about one week, although they can sometimes linger. Colds are caused by viruses different from those that cause influenza, and colds tend to be less severe than the flu. Children and people in poor health are most vulnerable to colds.

In the United States, most colds occur between September and May, when people tend to spend more time indoors, around others. This time of the year may also be more conducive to colds because of lower humidity (which helps colds to thrive) and because cold weather dries out the mucous membranes lining the inside of the nose, making the body more vulnerable to infection.

Cold viruses are highly contagious. People who have colds are most contagious during the first two to four days after symptoms appear and may be contagious for up to three weeks. The virus particles associated with colds can travel up to 12 feet (3.7 meters) through the air when an infected person coughs or sneezes.

Colds are often transmitted when a healthy person touches an infected person or an object (e.g., toy, phone, towel, utensils) that contains droplets of the cold virus. Once the cold virus is on the person’s fingers, it can then be introduced to the body through touching the eyes, nose or mouth. Infection also can be transmitted by inhaling infected airborne droplets.

The average adult gets two to four colds per year, according to the National Institutes of Health (NIH). Estimates vary for children, but according to the NIH, children experience between six and 10 colds each year, and school-age children may experience even more. The higher incidence of colds among children is due to a number of factors. Children have a less mature immune system and have not yet developed resistance to many viruses. They also spend long periods of time in close proximity to other children who are potentially infected. Finally, children tend to be less careful about washing their hands and adhering to other precautions that can help prevent cold transmission.

As people age, they tend to experience fewer colds as a result of their increased resistance to various viruses. People over the age of 60 average less than one cold per year, according to the NIH. However, certain people may remain at high risk for colds, including people who spend a lot of time in close contact with others, have allergies that affect the nasal passages, or are under psychological stress.

Women also tend to have more colds than men. This may be due to the amount of time women tend to spend with children because the increased incidence of colds is especially pronounced in women between the ages of 20 and 30.

More than 200 different viruses are known to cause colds, with rhinovirus being the most common source. Between 30 and 35 percent of all adult colds are caused by rhinoviruses, according to the National Institutes of Health (NIH). Science has identified more than 110 of these types of cold viruses, which grow best at about 91 degrees Fahrenheit (32.8 degrees Celsius), the approximate temperature inside the human nose.

Coronaviruses also are known to trigger many adult colds, especially during the winter and early spring. There are more than 30 types of coronaviruses, but just three or four affect humans.

More severe viral sources of colds include the parainfluenza virus and respiratory syncytial virus. While these viruses do not usually cause significant problems for adults, they can cause severe lower respiratory infections in young children.

About 10 to 15 percent of adult colds are caused by viruses that typically are responsible for more severe illnesses, according to the NIH.

Researchers are investigating the mechanisms behind the viruses that cause colds for a variety of reasons. They are working to understand how cold viruses infect the body and better ways to prevent or treat colds. Some scientists are even looking into using modified versions of certain cold viruses to help fight cancer without harming normal tissue.

Cold symptoms tend to appear about one to three days after the virus enters a person’s body. A cold usually lasts for about a week before clearing, although some colds may persist for longer periods of time.

Nasal discharge may become thicker and change color (e.g., to yellow or green) as the cold runs its course. In some cases, a low fever may also develop, particularly in infants and young children. However, unlike the flu, colds do not usually leave a person feeling fatigued.

It is often very difficult to identify whether a person has a cold or the flu based on symptoms alone. The National Institutes of Health has established a list of the symptoms that may help distinguish between the two conditions. These symptoms are:

Cold symptoms may be more severe among certain groups of people. For example, smokers are more likely to have more significant symptoms than nonsmokers. People with asthma, chronic bronchitis or emphysema (lung disease in which the air sacs are damaged) may notice that symptoms related to these conditions are worsened for weeks following a cold.

A cold infection also leaves the body vulnerable to other types of infections. These include bronchitis, ear infections and sinus infections. In addition, cold symptoms that last for more than one week may actually indicate the presence of a more serious illness, such as influenza or pneumonia.

People are urged to contact a physician if they experience abnormally severe cold symptoms or any of the following:

• Coughing that worsens even after other symptoms improve
• Ear pain
• High fever of at least 102 degrees Fahrenheit (38.9 degrees Celsius)
• Sinus headache
• Worsening of any pre-existing chronic lung problem

Usually, colds do not require the care of a physician and will disappear without treatment within a week or so. Nonetheless, more people visit physicians regarding cold symptoms than for any other illness, according to the American Lung Association. People should visit a physician if cold symptoms are unusually severe or persist for long periods of time.

A physician may perform a complete physical examination and compile a thorough medical history when diagnosing a cold. In addition, various tests may be performed to rule out other conditions that could be responsible for the patient’s symptoms.

There is no cure for the common cold. Antibiotics are ineffective in treating colds because these medications have no effect on viruses. Over-the-counter (OTC) medications used to treat colds include decongestants and antihistamines. Cough suppressants and combination medications that treat congestion, cough and nasal discharge also are available. Pain relief medications may also be used.

These OTC medications may help reduce the symptoms associated with colds. However, these drugs do not shorten the duration of colds and many experts advise against them because of side effects they may cause such as drowsiness, dizziness, insomnia or upset stomach. Medications such as decongestants can cause problems such as chronic inflammation of the mucous membranes lining the inside of the nose when used incorrectly. Some studies have shown that many of these medications provide minimal benefits, if any.

In addition, patients with certain medical conditions may be advised not to use certain types of cold relief medications. For example, people with thyroid disease, high blood pressure and other conditions should not take decongestants, and children should never take aspirin (which can cause Reye syndrome, a potentially fatal illness). People are urged to remember that no medication should be taken without first consulting a physician.

People with colds are urged to drink plenty of the right types of liquids. Eight glasses of water and/or juice per day are recommended to keep the lining of the nose and throat from drying out. This will keep mucus moist and easy to clear from the nose. In contrast, fluids that dehydrate the body should be avoided. These include alcohol and drinks that contain caffeine (e.g., coffee, tea or soft drinks).

It is also best to avoiding smoking and to stay away from others while they smoke. Inhaling smoke further irritates the throat, causing increased coughing.

Many supplements have been promoted as having the power to cure or prevent colds. These include echinacea, eucalyptus, garlic, honey, lemon, menthol, zinc, and vitamin C. To date, none of these products has been scientifically demonstrated to treat or prevent common colds.

There is no way to completely prevent the occurrence of a cold. However, avoiding close contact with people who have colds can substantially reduce the chances of becoming infected. It is particularly important to avoid exposure to cold germs during the first few days after a person becomes infected, when the condition is particularly contagious.

Frequent hand washing is another good way to reduce the risk of contracting a variety of infectious diseases, including a cold. Rhinoviruses, the most common cause of colds, can live for up to three hours on a person’s skin and on inanimate objects. It is particularly important to wash the hands after touching someone who has a cold or touching an object they have just touched. Using a disinfectant on contaminated objects also can significantly reduce the odds of spreading infection. Keeping one’s own fingers away from the mouth, nose and eyes also can reduce the odds of catching a cold, as viruses often enter the body in this manner.

Certain popular notions, such as the belief that a person can catch a cold by going outside with wet hair or simply being chilled on a cold day are not supported by science. However, managing stress levels is important because stress affects the immune system and may increase a person’s vulnerability to infection. In addition, regular exercise and a healthy diet help to boost immune system functioning and can help prevent colds from developing. Some studies have shown that a patient’s attitude may also affect his or her likelihood of catching a cold, as well as the severity of the symptoms if infection does occur. For example, people with an overall positive attitudes may suffer fewer and less severe colds than people with generally negative attitudes.

People who already have a cold can help prevent the spread of infection by using tissues when sneezing or coughing, immediately disposing of used tissues, and washing their hands frequently to avoid transmitting germs. It is also best that people with colds avoid physical contact with others who may be particularly susceptible to developing a cold. This includes young children, the elderly and anyone with chronic medical conditions such as asthma or chronic lung disease.