Colds are usually diagnosed clinically by the presence of typical symptoms including runny or stuffy nose, itchy or sore throat, dry cough, nasal congestion, facial pressure (sinuses), slight body aches or a mild headache, sneezing, itchy, watery eyes, low-grade fever (less than 102 degrees Fahrenheit), and mild fatigue (tiredness).
If the symptoms worsen after one to two weeks, a doctor will examine the individual's head, neck, and lungs, for signs and symptoms of more serious respiratory illnesses, such as pneumonia or bronchitis.
Upon presentation, a doctor may perform a throat culture or blood test to rule out infections secondary to bacteria such as Streptococcus (Strep throat).
Often confused with influenza, the common cold is caused by different types of viruses and usually does not result in a significantly higher body temperature. A high fever (above 102 degrees Fahrenheit) is a very reliable indicator of the flu. Hay fever may also cause many of the same symptoms as a cold, including runny or stuffy nose, cough, and scratchy throat.
Allergies to dander, dust, molds, or pollens (allergic rhinitis or hay fever) also can cause a runny nose, although this usually induces symptoms more persistent than the common cold,
signs and symptoms
Symptoms of a common cold usually appear about one to three days after exposure to a cold virus. Signs and symptoms of a common cold may include runny or stuffy nose, itchy or sore throat, dry cough, facial pressure due to sinuses (hollow bones in the front of the face), slight body aches or a mild headache, sneezing, itchy, watery eyes, low-grade fever (less than 102 degrees Fahrenheit), and mild fatigue (tiredness).
Nasal discharge may become thicker as a common cold runs its course. What makes a cold different from other viral infections (such as influenza) is that the individual generally will not have a high fever or colored sputum. They are also unlikely to experience significant fatigue from a common cold.
Colds last on average for one week. Mild colds may last only two or three days while severe colds may last for up to two weeks. Cough due to a cold can last for hours or days.
risk factors and causes
The cause of developing a cold is due to a viral infection, including rhinoviruses, coronaviruses, adenoviruses, echoviruses, respiratory syncytial viruses (RSV), and coxsackieviruses, which can infect the upper respiratory system. Although over a hundred different viruses can cause colds, 30-50% are caused by rhinoviruses.
The nose contains shelf-like structures called turbinates, which help trap particles (dust, dander, dirt, and viruses) entering the nasal passages. Material deposited in the nose is transported by cilia, which are hair-like structures that sweep particles to the back of the throat within 10-15 minutes of exposure. Viruses attach to receptors on epithelial (outer layer of skin) cells. In response to infection, the immune system triggers a series of events, including release of inflammatory cytokines (a group of proteins that help regulate inflammation, blood cell production, and immunity), such as interleukin-6 (IL-6), interleukin-8 (IL-8), and granulocyte-macrophage colony-stimulating factor or GMCSF), fluid leakage (runny nose), mucous membrane swelling (stuffy nose), increased mucous production, and stimulation of sneeze and cough reflexes. Nasal symptoms can begin as early as two hours after exposure, while cough and sore throat symptoms usually begin 10-12 hours following exposure to the virus. In the early stages of a cold, when the number of infecting viruses is still low, it may be possible for the body to build an effective immune response that prevents the cold from worsening. Keeping the number of viruses, called viral load, low decreases the ability of the cold virus to replicate (multiply) and cause infection.
The most common means of infection is from direct contact with the cold virus, such as an individual touching their skin to environmental surfaces (including telephones, computer keyboards, and stair rails) that have cold germs on them and then touching the eyes or nose. If an individual is physically exhausted or overtired, the chances of becoming a victim to the cold virus increase due to a impairment in immunity, or the decreased ability of the immune system to fight off infection.
Colds are also easily transmitted (by coughing or sneezing) by inhaling droplets of mucus contaminated with cold viruses. Mucus is a thick, slippery secretion of the inner lining or organs (called mucous membranes) in the body including the nostril, ears, anus, and lips. The cold virus is spread when the infected mucus drops come in contact with other individual's noses and eyes, occurring this way more frequently than through the mouth.
Social activity: Individuals exposed to large amounts of people during the day are also exposed to many viruses. Children attending school or playing with other kids, traveling in airplanes or buses, and having large families increases the risk of exposure to a cold virus. Being around people that are sneezing and coughing increases the chances for getting a cold virus. Touching things that others frequently touch, such as railings and doors in public facilities, also increases the chances of developing a cold. An individual's work place may also increase their chances of exposure to a cold virus. Healthcare workers (such as nurses, pharmacists, and doctors), day care workers, people that work in retail stores, and individuals in public office are exposed to many people daily, where the chances of viral exposure and developing a cold is increased.
Children and infants (less than 14 years of age) are especially susceptible to colds. Their immune systems have not yet become adjusted to being exposed to various cold viruses and have not yet developed resistance to the viruses commonly encountered. Children also may not be as careful about cleanliness such as hand washing. Children tend to spend lots of time with other children (at play and school), making it easy for colds to spread. As they age, immunity develops for many of the common viruses that cause colds. Colds will generally occur less frequently with age.
Seasonal changes: Both children and adults seem to be most susceptible to colds in fall and winter. In cold months when the air is very dry, people turn on their heating systems, drying the air even more. Dry air dehydrates the mucous membranes in the nose and throat, which are the first line of defense against the viruses. This allows the viruses to attack the tissue in the nose and throat. Individuals working in air conditioned offices tend to have more summer colds than people who do not work in air conditioned environments. Air conditioning dries out the air and the mucous membranes and can circulate viruses in the air.
Environmental toxins: The risk of respiratory infections is increased by exposure to environmental toxins, including cigarette smoke, which can injure airways and damage the cilia (tiny hair-like structures that help keep the airways clear). Physically engaging in smoking or breathing in passive (second hand) smoke can damage the cilia. Toxic fumes, industrial smoke, and other air pollutants are also environmental risk factors.
Lowered immunity: Individuals with lowered immunity, such as those with the human immunodeficiency virus (HIV) or cancer, and individuals taking certain medications such as chemotherapy, are at greater risk of developing colds. Colds can be severe in these individuals, due to poor immune status.
Medications: Drug therapies, including corticosteroid (steroid) treatments, chemotherapy, or other medications that suppress the immune system also increase the risk of developing an infection from a cold virus.
Stress: Stress can lower the resistance to infection by depressing the immune system Stress causes the adrenal glands to increase the production of the stress hormone called cortisol. During normal stressful circumstances, cortisol production is a healthy response of the body. Chronic (long-term) stress, however, causes the levels of cortisol to stay increased, leading to decreased immunity, hyperinsulinemia (the inability of the body to process insulin), and an increase in blood pressure. Stress during menopause may also increase the chances of catching a cold due to impaired immunity.
Too much exercise: High-intensity or endurance exercises appear to suppress the immune system while they are being performed. Some highly trained athletes, for instance, report being susceptible to colds after strenuous exercise.
Malnutrition: Low vitamin and mineral levels, such as vitamins A, E, C, the B vitamins, selenium, and zinc, may decrease immunity and increase the chances of getting a cold. Very low fat diets also appear to lower the immune system.
Lack of sleep: Sleep helps the body recharge. Proper sleep (eight hours of uninterrupted sleep for an adult) can help keep the body's immune system healthy and fight off colds.
Bacterial infections: Colds can occasionally lead to bacterial infections of the middle ear, throat, or sinuses, requiring treatment with antibiotics. High fever (greater than 102 degrees Fahrenheit), significantly swollen glands, severe sinus pain, and a cough that produces colored mucus, may indicate a complication or more serious illness requiring a visit to a doctor. Colds also can produce colored mucus, and a doctor will have to determine if the mucus is infected from a cold virus or another infection, such as influenza or bacteria. Samples of the mucus are taken and studied under a microscope to determine the exact cause of the infection.
Sinusitis: Between 0.5% and five percent of people with colds develop sinusitis, an infection in the sinus cavities (air-filled spaces in the front of the skull), including pressure, nasal stuffiness, and headache. Sinusitis is usually mild, but if it becomes severe, antibiotics generally eliminate further problems. In rare cases, however, sinusitis can be serious.
Bronchitis and pneumonia: The common cold poses a risk for bronchitis and pneumonia in nursing home patients and other people who may be susceptible to infection. Some experts believe that the rhinovirus may play a more significant role than the flu in causing lower respiratory infections in such individuals.
Wheezing: Rhinovirus infection often triggers asthma attacks in individuals with asthma.
Acute ear infection (otitis media): The most frequent complication of common colds in children is otitis media, or an ear infection in which bacteria infect the space behind the eardrum. Typical signs and symptoms of otitis media include earaches and, in some cases, green or yellow discharge from the nose, or the return of a fever following a common cold. Children who are too young to verbalize their distress may simply cry or pull on the affected ear.