Sneezing, scratchy throat, runny nose – everyone knows the first signs of a cold, probably the most common illness known. Although the common cold is usually mild, with symptoms lasting one to two weeks, it is a leading cause of doctor visits and of school and job absenteeism.
In the course of a year, individuals in the United States suffer 1 billion colds, according to some estimates.
Adults average about two to four colds a year, although the range varies widely. Women, especially those aged 20 to 30 years, have more colds than men.
The Viruses. More than 200 different viruses are known to cause the symptoms of the common cold. Some, such as the rhinoviruses, seldom produce serious illnesses. Others, such as parainfluenza and respiratory syncytial virus, produce mild infections in adults but can precipitate severe lower respiratory infections in young children.
Rhinoviruses (from the Greek rhin, meaning "nose") cause an estimated 30 to 35 percent of all adult colds, and are most active in early fall, spring and summer. More than 110 distinct rhinovirus types have been identified. These agents grow best at temperatures of 33 degrees Celsius [about 91 degrees Fahrenheit (F)], the temperature of the human nasal mucosa.
Coronaviruses are believed to cause a large percentage of all adult colds. They induce colds primarily in the winter and early spring. Of the more than 30 isolated strains, three or four infect humans. The importance of coronaviruses as causative agents is hard to assess 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), paramyxoviruses (including several parainfluenza viruses), respiratory syncytial virus and enteroviruses.
The causes of 30 to 50 percent 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 pediatric colds, however, is unclear because of the difficulty in isolating the precise cause of symptoms in studies of children with colds.
Does cold weather cause a cold? Although many people are convinced that a cold results from exposure to cold weather, or from getting chilled or overheated, NIAID grantees have found that these conditions have little or no effect on the development or severity of a cold. Nor is susceptibility apparently related to factors such as exercise, diet, or enlarged tonsils or adenoids. On the other hand, research suggests that psychological stress, allergic disorders affecting the nasal passages or pharynx (throat), and menstrual cycles may have an impact on a person's susceptibility to colds.
The Cold Season
In the United States, most colds occur during the fall and winter. Beginning in late August or early September, the incidence of colds increases slowly for a few weeks and remains high until March or April, when it declines. The seasonal variation may relate to the opening of schools and to cold weather, which prompt people to spend more time indoors and increase the chances that viruses will spread from person to person.
Seasonal changes in relative humidity also may affect the prevalence of colds. The most common cold-causing viruses survive better when humidity is low—the colder months of the year. Cold weather also may make the nasal passages' lining drier and more vulnerable to viral infection.
Symptoms of the common cold usually begin two to three days after infection and often include nasal discharge, obstruction of nasal breathing, swelling of the sinus membranes, sneezing, sore throat, cough, and headache. Fever is usually slight but can climb to 102° F in infants and young children. Cold symptoms can last from two to 14 days, but two-thirds of people recover in a week. If symptoms occur often or last much longer than two weeks, they may be the result of an allergy rather than a cold.
Colds occasionally can lead to secondary bacterial infections of the middle ear or sinuses, requiring treatment with antibiotics. High fever, significantly swollen glands, severe facial pain in the sinuses, and a cough that produces mucus, may indicate a complication or more serious illness requiring a doctor's attention.
How Colds are Spread
Depending on the virus type, any or all of the following routes of transmission may be common:
- touching infectious respiratory secretions on skin and on environmental surfaces and then touching the eyes or nose;
- inhaling relatively large particles of respiratory secretions transported briefly in the air;
- inhaling droplet nuclei: smaller infectious particles suspended in the air for long periods of time.
Handwashing is the simplest and most effective way to keep from getting rhinovirus colds. Not touching the nose or eyes is another. Individuals with colds should always sneeze or cough into a facial tissue, and promptly throw it away. If possible, one should avoid close, prolonged exposure to persons who have colds.
Because rhinoviruses can survive up to three hours outside the nasal passages on inanimate objects and skin, cleaning environmental surfaces with a virus-killing disinfectant might help prevent spread of infection.
Only symptomatic treatment is available for uncomplicated cases of the common cold: bed rest, plenty of fluids, gargling with warm salt water, petroleum jelly for a raw nose, and aspirin or acetaminophen to relieve headache or fever.
A word of caution: several studies have linked the use of aspirin to the development of Reye's Syndrome in children recovering from influenza or chicken pox. Reye's syndrome is a rare but serious illness that usually occurs in children between the ages of three and 12 years. It can affect all organs of the body, but most often injures the brain and liver. While most children who survive an episode of Reye's Syndrome do not suffer any lasting consequences, the illness can lead to permanent brain damage or death. The American Academy of Pediatrics recommends children and teenagers not be given aspirin or any medications containing aspirin when they have any viral illness, particularly chicken pox or influenza. Many doctors recommend these medications be used for colds in adults only when headache or fever is present. Researchers, however, have found that aspirin and acetaminophen can suppress certain immune responses and increase nasal stuffiness in adults.
Nonprescription cold remedies, including decongestants and cough suppressants, may relieve some cold symptoms but will not prevent, cure, or even shorten the duration of illness. Moreover, most have some side effects, such as drowsiness, dizziness, insomnia, or upset stomach, and should be taken with care.
Nonprescription antihistamines may have some effect in relieving inflammatory responses such as runny nose and watery eyes that are commonly associated with colds.
Antibiotics do not kill viruses. These prescription drugs should be used only for rare bacterial complications, such as sinusitis or ear infections, that can develop as secondary infections. The use of antibiotics "just in case" will not prevent secondary bacterial infections.
Does vitamin C have a role? Many people are convinced that taking large quantities of vitamin C will prevent colds or relieve symptoms. To test this theory, several large-scale, controlled studies involving children and adults have been conducted. To date, no conclusive data has shown that large doses of vitamin C prevent colds. The vitamin may reduce the severity or duration of symptoms, but there is no definitive evidence.
Taking vitamin C over long periods of time in large amounts may be harmful. Too much vitamin C can cause severe diarrhea, a particular danger for elderly people and small children. In addition, too much vitamin C distorts results of tests commonly used to measure the amount of glucose in urine and blood. Combining oral anticoagulant drugs and excessive amounts of vitamin C can produce abnormal results in blood-clotting tests.
Inhaling steam also has been proposed as a treatment of colds on the assumption that increasing the temperature inside the nose inhibits rhinovirus replication. Recent studies found that this approach had no effect on the symptoms or amount of viral shedding in individuals with rhinovirus colds. But steam may temporarily relieve symptoms of congestion associated with colds.
Interferon-alpha has been studied extensively for the treatment of the common cold. Investigators have shown interferon, given in daily doses by nasal spray, can prevent infection and illness. Interferon, however, causes unacceptable side effects such as nosebleeds and does not appear useful in treating established colds. Most cold researchers are concentrating on other approaches to combating cold viruses.
NIAID is a component of the National Institutes of Health (NIH), which is an agency of the Department of Health and Human Services. NIAID supports basic and applied research to prevent, diagnose, and treat infectious and immune-mediated illnesses, including HIV/AIDS and other sexually transmitted diseases, illness from potential agents of bioterrorism, tuberculosis, malaria, autoimmune disorders, asthma and allergies.
News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site.
Office of Communications and Public Liaison
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, MD 20892
The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is to get a flu vaccine each fall.
Every year in the United States, on average:
- 5% to 20% of the population gets the flu;
- more than 200,000 people are hospitalized from flu complications; and
- approximately 36,000 people die from flu.
Some people are at high risk for serious flu complications, such as older people, young children, and people with certain health conditions, including pregnancy.
Symptoms & Complications of Flu
Symptoms of flu include:
- fever (usually high)
- extreme tiredness
- dry cough
- sore throat
- runny or stuffy nose
- muscle aches
- gastro-intestinal symptoms, such as nausea, vomiting, and diarrhea, are much more common among children than adults.
Some of the complications caused by flu include bacterial pneumonia, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. Children may get sinus problems and ear infections.
How Flu Spreads
The flu spreads in respiratory droplets caused by coughing and sneezing. It usually spreads from person to person, though occasionally a person may become infected by touching an infected surface and then touching their mouth or nose.
Adults may be able to infect others beginning one day before getting symptoms and up to seven days after getting sick. That means that you can give someone the flu before you know you’re sick as well as while you are sick.
Good Health Habits
- Avoid close contact.
Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.
- Stay home when you are sick.
If possible, stay home from work, school, and errands when you are sick. You will help prevent others from catching your illness.
- Cover your mouth and nose.
Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick.
- Clean your hands.
Washing your hands often will help protect you from germs.
- Avoid touching your eyes, nose, or mouth.
Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth.
Information from: www.cdc.gov
Tension headaches: The most common type of headache is "tension headache." Tension headaches generally develop gradually and often involve the entire head as well as the neck and shoulders. They probably are not actually caused by increased muscle tension, although muscle relaxation techniques can be very useful in treatment. Most people get tension headaches occasionally and these can usually be treated simply. Some people get them often, but there are usually some useful interventions to help decrease the number of sick days.
Migraine headaches: are "bad headaches." With classic migraine, the headache is preceded by a feeling that a headache will develop (prodrome) followed by visual phenomena such as dark or bright spots, streaks of light, or tunnel vision (aura). The headache then develops, usually on one side. It is throbbing in nature, accompanied by nausea and increased sensitivity to light and noise.
Most people with migraine headaches do not experience prodrome or aura. Common migraine headache, like classic migraine headache, is treatable and often preventable.
Cluster headaches are headaches lasting minutes to hours that occur day after day at a similar time over a period of weeks. They are sharp. People with cluster headaches often describe the pain as similar to an ice pick.
They are more common in men, and are more difficult to treat than most headaches. Interestingly, oxygen therapy will often stop a daily cluster headache. Many of the medications used to prevent or treat migraine headaches are used to treat cluster headaches.
Sinus headaches are those frontal headaches that some people experience with sinus infection and with changes in the weather. Allergies can also provoke them.
To avoid headaches, employ good health habits. These include adequate sleep, healthy diet, regular exercise and good stress management. Quitting smoking is essential in reducing the risks for all headaches.
Relaxation and related stress reduction therapies can diminish the frequency and intensity of headaches. Alternative therapies used for headache management include hypnosis, biofeedback, meditation, visualization and guided imagery, acupuncture, accupressure, yoga, and other physical relaxation exercises.
Any over-the-counter pain medications like aspirin, ibuprofen, naproxen sodium or acetaminophen can be very useful. No one medication has ever been proven to be more effective than the other, though there is great variability in effectiveness from person to person.
Headache as a Warning Sign
Go to the Student Health Center if any of the following occur:
- Severe, sudden headaches that seem to come on like "a bolt out of the blue";
- Headaches that are accompanied by a loss of consciousness, alertness or sensation, confusion, or other neurological and/or personality changes;
- Headaches that recur in one particular area such as an eye, temple etc.;
- Headaches that recur and are of high intensity or frequency;
- Headaches that are accompanied by neck stiffness and fever;
- Headaches that are associated with head injury;
- There is a change in the nature or frequency of headaches;
- The worst headache in one's life;
- Temporary change in vision or visual acuity may simply be a sign of migraine headache but deserves special attention if new.
Information from: American Council for Headache Education