Causes of common cold

The common cold is a self-limited contagious illness that can be caused by a number of different types of viruses. The common cold is medically referred to as a viral upper respiratory tract infection. Symptoms of the common cold may include cough, sore throat, nasal congestion, runny nose, and sneezing. More than 200 different types of viruses are known to cause the common cold, with rhinovirus causing approximately 30%-35% of all adult colds. Other commonly implicated viruses include coronavirus, adenovirus, respiratory syncytial virus, and parainfluenza virus. Because so many different viruses can cause the common cold and because new cold viruses constantly develop, the body never builds up resistance against all of them. For this reason, colds are a frequent and recurring problem. In fact, children in preschool and elementary school can have six to 12 colds per year while adolescents and adults typically have two to four colds per year. The common cold occurs most frequently during the fall and winter months.
The common cold is the most frequently occurring illness in the world, and it is a leading cause of doctor visits and missed days from school and work. It is estimated that individuals in the United States suffer 1 billion colds per year, with approximately 22 million days of school absences recorded annually. In the United States, the common cold is thought to account for approximately 75-100 million physician visits annually, with an economic impact of greater than $20 billion per year due to cold-related work loss.
How is the common cold transmitted?
The common cold is spread either by direct contact with infected secretions from contaminated surfaces or by inhaling the airborne virus after individuals sneeze or cough. Person-to-person transmission often occurs when an individual who has a cold blows or touches their nose and then touches someone or something else. A healthy individual who then makes direct contact with these secretions can

subsequently become infected, often after their contaminated hands make contact with their own eyes, nose, or mouth. A cold virus can live on objects such as pens, books, telephones, computer keyboards, and coffee cups for several hours and can thus be acquired from contact with these objects.
What are risk factors for acquiring the common cold?
There are various factors that may increase the chances of acquiring the common cold, including the following:
* Age: Infants and young children are more likely to develop the common cold because they have not yet developed immunity to many of the implicated viruses.
* Seasonal variation: Individuals more commonly acquire the common cold during the fall and winter, or during the rainy season (in warmer climates). This is felt to occur because people tend to stay indoors and are in closer proximity to one another.
* Weakened immune system: Individuals with a poorly functioning immune system are more likely to develop the common cold.
What are the symptoms and signs of the common cold in adults, children, and infants?
The symptoms of the common cold typically begin two to three days after acquiring the infection (incubation period), though this may vary depending on the type of virus causing the infection. Symptoms and signs of the common cold may also vary depending on the virus responsible for the infection and may include
* nasal stuffiness or drainage,
* sore or scratchy throat,
* sneezing,
* hoarseness,
* cough,
* watery eyes,
* low-grade fever,
* headache,
* body aches,
* fatigue.
The signs and symptoms of the common cold in infants and children are similar to those seen in adults. The cold may begin with a runny nose with clear nasal discharge, which later may become yellowish or greenish in color. Infants and children may also become more fussy and have decreased appetite.
Does it have anything to do with exposure to cold weather?
Though the common cold usually occurs in the fall and winter months, the cold weather itself does not cause the common cold. Rather, it is thought that during cold-weather months, people spend more time indoors in close proximity to each other, thus facilitating the spread of the virus. For this same reason, children in day care and school are particularly prone to acquiring the common cold.
What is the difference between the common cold and influenza (the flu)?
Many people confuse the common cold with influenza (the flu). Influenza is caused by the influenza virus, while the common cold generally is not. While some of the symptoms of the common cold and influenza may be similar, patients with the common cold typically have a milder illness. Patients with influenza usually appear more ill and have a more abrupt onset of illness with fever, chills, headache, substantial muscle and body aches, dry cough, and extreme weakness.
Though differentiating between the common cold and influenza can be difficult, there is laboratory testing available to confirm the diagnoses of influenza.
How do physicians diagnose the common cold?
A physician or health-care professional will generally diagnose the common cold based on the description of the symptoms and the findings during the physical exam. Laboratory testing and imaging studies are generally not necessary unless there are concerns about another underlying medical condition or potential complications.
What is the treatment for the common cold? Are there any home remedies for the common cold?
There is no cure for the common cold. The common cold is a self-limited illness that will resolve spontaneously with time and expectant management. Home remedies and treatments are directed at alleviating the symptoms associated with the common cold while the body fights off the infection.
Home treatment for the common cold includes getting rest and drinking plenty of fluids. In older children and adults, over-the-counter medications such as throat lozenges, throat sprays, cough drops, and cough syrups may help relieve symptoms, though they will not prevent or shorten the duration of the common cold. Gargling with warm saltwater may help those with a sore throat. Decongestants such as pseudoephedrine (Sudafed) or antihistamines may be used for nasal symptoms, while saline nasal sprays may also be beneficial. It is important to note that over-the-counter medications may cause undesirable side effects, therefore they must be taken with care as directed.
Are antibiotics a suitable treatment for the common cold?
No. Antibiotics play no role in treating the common cold. Antibiotics are effective only against illnesses caused by bacteria, and colds are caused by viruses. Not only do antibiotics not help, but they can rarely also cause severe allergic reactions that can sometimes be fatal. Furthermore, using antibiotics when they are not necessary has led to the growth of several strains of common bacteria that have become resistant to certain antibiotics. For these and other reasons, it is important to limit the use of antibiotics to situations in which they are medically indicated.
Occasionally, a bacterial infection such as sinusitis or a middle ear infection can develop following the common cold, however the decision to treat with antibiotics should be determined by a physician or health-care professional after a medical evaluation.
When should a health-care professional be consulted?
Generally, the common cold can be treated at home and managed with over-the-counter medications. However, if more severe symptoms develop, such as shaking chills, high fever (greater than 102 F), severe headache, neck stiffness, vomiting, abdominal pain, difficulty breathing, chest pain, confusion, or failure to improve after 10 days, consult a health-care professional immediately. Infants 3 months of age or younger who develop a cold or fever should be seen by their health-care professional as well.
If a sore throat and a fever are present with no other cold symptoms, the individual should also be evaluated by a health-care professional. This illness may be strep throat, a bacterial infection requiring treatment with antibiotics.
Finally, if there is facial pain and yellow/green drainage from the nose accompanied by a fever, it is possible that the individual has a sinus infection (sinusitis) that would benefit from a medical evaluation and a possible course of antibiotics.
What is the prognosis for the common cold?
Generally, the prognosis for the common cold is excellent. The common cold needs to run its natural course, and most individuals with the common cold will recover within seven to 10 days.
What are complications of the common cold?
Complications that may arise from the common cold include the development of a middle ear infection (otitis media) or sinusitis. In individuals with asthma or chronic obstructive pulmonary disease (COPD), the common cold can sometimes trigger an exacerbation of their illness, leading to shortness of breath and increased wheezing. Though uncommon, pneumonia can sometimes develop as a secondary infection in individuals with the common cold.
Is it possible to prevent the common cold?
The most important measure to prevent the common cold is to avoid contact with infected individuals. Other measures to help prevent the common cold include the following:
* Frequent and thorough hand washing is extremely important, as this can destroy viruses acquired from touching contaminated surfaces.
* Disinfect potentially infected surfaces or personal objects, and do not share personal belongings such as towels.
* Avoid sharing utensils and try to use disposable items (such as disposable cups) if someone in the family has a cold.
* Encourage individuals to cover their nose and mouth when coughing or sneezing to prevent transmission of the virus.
* Lifestyle modifications such as smoking cessation and stress management may decrease susceptibility to acquiring the common cold.