COMMON COLD DEFINITION
The common cold is a viral infection of your upper respiratory tract — your nose and throat. A common cold is usually harmless, although it may not feel that way at the time. If it’s not a runny nose, sore throat and cough, it’s the watery eyes, sneezing and congestion — or maybe all of the above. In fact, because any one of more than 100 viruses can cause a common cold, signs and symptoms tend to vary greatly.
Preschool children are at greatest risk of frequent colds, but even healthy adults can expect to have a few colds each year.
Most people recover from a common cold in about a week or two. If symptoms don’t improve, see your doctor.
COMMON COLD CAUSES
You can catch it from another person who is infected with the virus. This usually happens if you touch a surface that has germs on it — a computer keyboard, doorknob, or spoon, for example — and then touch your nose or mouth. You can also catch it if you’re near someone who is sick and sneezes into the air.
A cold begins when a virus attaches to the lining of your nose or throat. Your immune system — the body’s defense against germs — sends out white blood cells to attack this invader. Unless you’ve had a run-in with that exact strain of the virus before, the initial attack fails and your body sends in reinforcements. Your nose and throat get inflamed and make a lot of mucus. With so much of your energy directed at fighting the cold virus, you’re left feeling tired and miserable.
One myth that needs to get busted: Getting chilly or wet doesn’t cause you to get sick. But there are things that make you prone to come down with a cold. For example, you’re more likely to catch one if you’re extremely tired, under emotional distress, or have allergies with nose and throat symptoms.
COMMON COLD PATHOPHYSIOLOGY
RV possesses various transmission modes and can infect a huge population at any given time. Most commonly, RVs are transmitted to susceptible individuals through direct contact or via aerosol particles. The primary site of inoculation is the nasal mucosa, though the conjunctiva may be involved to a lesser extent. RV attaches to respiratory epithelium and spreads locally. The major human RV receptor is ICAM-1 (found in high quantities in the posterior nasopharynx).
Highly contagious behavior includes nose blowing, sneezing, and physically transferring infected secretions onto environmental surfaces or paper tissue. Contrary to popular belief, behaviors such as kissing, talking, coughing, or even drooling do not contribute substantially to the spread of disease.
Infection rates approximate 50% within the household and range from 0% to 50% within schools, indicating that transmission requires long-term contact with infected individuals. Brief exposures to others in places such as movie theaters, shopping malls, friends’ houses, or doctors’ offices are associated with a low risk of transmission. Because children produce antibodies to fewer serotypes, those who attend school are the most common reservoirs of RV infection.
Pathogenesis of infection
The natural response of the human defense system to injury involves ICAM-1, which aids the binding between endothelial cells and leukocytes. RV takes advantage of ICAM-1 by using it as a receptor for attachment. In addition, it uses ICAM-1 for subsequent viral uncoating during cell invasion. Some RV serotypes also upregulate ICAM-1 expression on human epithelial cells to increase susceptibility to infection.
Few cells are actually infected by RV, and the infection involves only a small portion of the epithelium. Symptoms develop 1-2 days after viral infection, peaking 2-4 days after inoculation, though reports have described symptoms as early as 2 hours after inoculation with primary symptoms 8-16 hours later. Viremia is uncommon.
A local inflammatory response to RV in the respiratory tract can lead to nasal discharge, nasal congestion, sneezing, and throat irritation. The nasal epithelium is not damaged. Various polymorphisms in cytokine genes have been shown to impact the severity of rhinovirus infection, suggesting a genetic predisposition.Detectable histopathology causing the associated nasal obstruction, rhinorrhea, and sneezing is lacking, which leads to the hypothesis that the host immune response plays a major role in the pathogenesis.
Infected cells release interleukin (IL)–8, which is a potent chemoattractant for polymorphonuclear leukocytes (PMNs). Concentrations of IL-8 in secretions correlate proportionally with the severity of common cold symptoms. Inflammatory mediators, such as kinins and prostaglandins, may cause vasodilatation, increased vascular permeability, and exocrine gland secretion. These, together with local parasympathetic nerve-ending stimulation, lead to cold symptoms.
Deficient production of interferon beta by asthmatic bronchial epithelial cells has been proposed as a mechanism for increased susceptibility to RV infections in individuals with asthma.
Viral clearance is associated with the host response and is due in part to the local production of nitric oxide. RV is shed in large amounts, with as many as 1 million infectious virions present per milliliter of nasal washings. Viral shedding can occur a few days before cold symptoms are recognized by the patient, peaks on days 2-7 of the illness, and may last as long as 3-4 weeks.
Serotype-specific neutralizing antibodies are found 7-21 days after infection in 80% of patients. Although these antibodies persist for years, providing long-lasting immunity, recovery from illness is more likely related to cell-mediated immunity. Persistent protection from repeat infection by that serotype appears to be partially attributable to immunoglobulin A (IgA) antibodies in nasal secretions, serum immunoglobulin G (IgG), and, possibly, serum immunoglobulin M (IgM).
Clinical studies indicate sinus involvement in common colds. Abnormal computed tomography (CT) findings (eg, opacification, air-fluid levels, and mucosal thickening) are present in adults with common colds that resolve over 1-2 weeks without antibiotic therapy.
Despite what is reported in folklore, no good clinical evidence suggests that colds are acquired by exposure to cold weather, getting wet, or becoming chilled.
COMMON COLD SYMPTOMS
Symptoms of a common cold usually appear about one to three days after exposure to a cold-causing virus. Signs and symptoms of a common cold may include:
- Runny or stuffy nose
- Itchy or sore throat
- Slight body aches or a mild headache
- Watery eyes
- Low-grade fever
- Mild fatigue
The discharge from your nose may become thicker and yellow or green in color as a common cold runs its course. What makes a cold different from other viral infections is that you generally won’t have a high fever. You’re also unlikely to experience significant fatigue from a common cold.
When to see a doctor
For adults — seek medical attention if you have:
- Fever of 103 F (39.4 C) or higher
- Fever accompanied by sweating, chills and a cough with colored phlegm
- Significantly swollen glands
- Severe sinus pain
For children — in general, children are sicker with a common cold than adults are and often develop complications, such as ear infections. Your child doesn’t need to see the doctor for a routine common cold. But seek medical attention right away if your child has any of the following signs or symptoms:
- Fever of 100.4 F (38 C) in newborns up to 12 weeks
- Fever that rises repeatedly above 104 F (40 C) in a child of any age
- Signs of dehydration, such as urinating less often than usual
- Not drinking adequate fluids
- Fever that lasts more than 24 hours in a child younger than 2
- Fever that lasts more than three days in a child older than 2
- Vomiting or abdominal pain
- Unusual sleepiness
- Severe headache
- Stiff neck
- Difficulty breathing
- Persistent crying
- Ear pain
- Persistent cough
COMMON COLD DIAGNOSIS
Usually you don’t need to see a doctor for a cold. But if your symptoms continue, it’s important to see your doctor. Learn when it’s time to see the doctor to determine if your cold has turned into something worse.
COMMON COLD TREATMENT
There’s no cure for the common cold. Antibiotics are of no use against cold viruses. Over-the-counter (OTC) cold preparations won’t cure a common cold or make it go away any sooner, and most have side effects. Here’s a look at the pros and cons of some common cold remedies.
- Pain relievers. For fever, sore throat and headache, many people turn to acetaminophen (Tylenol, others) or other mild pain relievers. Keep in mind that acetaminophen can cause liver damage, especially if taken frequently or in larger than recommended doses. Don’t give acetaminophen to children under 3 months of age, and be especially careful when giving acetaminophen to older babies and children because the dosing guidelines can be confusing. For instance, the infant-drop formulation is much more concentrated than the syrup commonly used in older children. Use caution when giving aspirin to children or teenagers. Though aspirin is approved for use in children older than age 2, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This is because aspirin has been linked to Reye’s syndrome, a rare but potentially life-threatening condition, in such children.
- Decongestant nasal sprays. Adults shouldn’t use decongestant drops or sprays for more than a few days because prolonged use can cause chronic rebound inflammation of mucous membranes. And children shouldn’t use decongestant drops or sprays at all. There’s little evidence that they work in young children, and they may cause side effects.
- Cough syrups. The Food and Drug Administration (FDA) and the American Academy of Pediatrics strongly recommend against giving OTC cough and cold medicines to children younger than age 2. Over-the-counter cough and cold medicines don’t effectively treat the underlying cause of a child’s cold, and won’t cure a child’s cold or make it go away any sooner. These medications also have potential side effects, including rapid heart rate and convulsions.
FDA experts are studying the safety of cough and cold medicines for children older than age 2. In the meantime, remember that cough and cold medicines won’t make a cold go away any sooner — and side effects are still possible. If you give cough or cold medicines to an older child, carefully follow the label directions. Don’t give your child two medicines with the same active ingredient, such as an antihistamine, decongestant or pain reliever. Too much of a single ingredient could lead to an accidental overdose.