Common cold

The typical symptoms of a cold include cough, runny nose, sneezing, nasal congestion, and a sore throat, sometimes accompanied by muscle ache, fatigue, headache, and loss of appetite. A sore throat is present in about 40% of cases, a cough in about 50%, A number of the viruses that cause the common cold may also result in asymptomatic infections. The color of the mucus or nasal secretion may vary from clear to yellow to green and does not show whether the infection is viral or bacterial. Progression A cold usually begins with fatigue, a feeling of being chilled, sneezing, and a headache, followed in a couple of days by a runny nose and cough. and typically peak two to four days after onset. They usually resolve in seven to ten days, but some can last for up to three weeks. and in some cases people develop a post-viral cough which can linger after the infection is gone. In children, the cough lasts for more than ten days in 35–40% of cases and continues for more than 25 days in 10%. ==Causes==

Viruses es are a group of viruses known for causing the common cold. They have a halo or crown-like (corona) appearance when viewed under an electron microscope. The common cold is an infection of the upper respiratory tract which can be caused by many different viruses. The most common are rhinoviruses (up to 40%) which have over 100 known serotypes (variations). Other common viruses include coronaviruses, adenoviruses, enteroviruses, parainfluenza, and RSV. Frequently, more than one virus is present. In total, more than 200 viral types are associated with colds. Breathing, talking, or coughing causes an infected individual to release small droplets which carry the virus. These droplets can directly infect someone if they are inhaled or come in contact with their eyes or nose. Transmission is common in daycare and schools due to the proximity of many children with little immunity and poor hygiene. There is no evidence that recirculated air during commercial flight is a method of transmission. Other Herd immunity, generated from previous exposure to cold viruses, plays an important role in limiting viral spread, as seen with younger populations that have greater rates of respiratory infections. Insufficient sleep and malnutrition have been associated with a greater risk of developing infection following rhinovirus exposure; this is believed to be due to their effects on immune function. A mother with the common cold cannot transmit it through her breast milk, and by the time she is showing symptoms the baby has already been exposed to the virus. As such it is recommended a breastfeeding mother with a cold continue breastfeeding. In the developed world, breastfeeding may not be protective against the common cold in and of itself. ==Pathophysiology==

. The symptoms of the common cold are believed to be primarily related to the immune response to the virus. RSV does cause epithelium damage. In young children, when it affects the trachea, it may produce the symptoms of croup, due to the small size of their airways. ==Diagnosis==

The distinction between viral upper respiratory tract infections is loosely based on the location of symptoms, with the common cold affecting primarily the nose (rhinitis), throat (pharyngitis), and lungs (bronchitis). and it is generally not possible to identify the virus type through symptoms. ==Prevention==

The only useful ways to reduce the spread of cold viruses are physical and engineering measures Vaccination has proven difficult as there are so many viruses involved and because they mutate rapidly. Creation of a broadly effective vaccine is, therefore, highly improbable. Regular hand washing appears to be effective in reducing the transmission of cold viruses, especially among children. Whether the addition of antivirals or antibacterials to normal hand washing provides greater benefit is unknown. ==Management==

There is no cure for the common cold. Treatment for the common cold primarily involves medications and other therapies to relieve symptoms. Much of the benefit from symptomatic treatment is, however, attributed to the placebo effect. no medications or herbal remedies had been conclusively demonstrated to shorten the duration of infection. Symptomatic Treatments that may help with symptoms include pain medication and medications for fevers such as ibuprofen However, it is not clear whether acetaminophen helps with symptoms. It is not known if over-the-counter cough medications are effective for treating an acute cough. Cough medicines are not recommended for use in children due to a lack of evidence supporting effectiveness and the potential for harm. In 2009, Canada restricted the use of over-the-counter cough and cold medication in children six years and under due to concerns regarding risks and unproven benefits. Intranasal corticosteroids have not been found to be useful. In adults, short term use of nasal decongestants may have a small benefit. Other decongestants such as pseudoephedrine appear effective in adults. Combined oral analgesics, antihistaminics, and decongestants are generally effective for older children and adults. Ipratropium nasal spray may reduce the symptoms of a runny nose but has little effect on stuffiness. Ipratropium may also help with coughs in adults. The safety and effectiveness of nasal decongestant use in children is unclear. As of 2017, heated and humidified air, such as via RhinoTherm, is of unclear benefit. One study has found chest vapor rub to provide some relief of nocturnal cough, congestion, and sleep difficulty. Some experts advise against physical exercise if there are symptoms such as fever, widespread muscle aches, or fatigue. It is regarded as safe to perform moderate exercise if the symptoms are confined to the head, including runny nose, nasal congestion, sneezing, or a minor sore throat. Antibiotics and antivirals Antibiotics have no effect against viral infections, including the common cold. Due to their side effects, antibiotics cause overall harm but nevertheless are still frequently prescribed. The common prescription of antibiotics for colds significantly increases the development of antibiotic resistance. There are no effective antiviral drugs for the common cold even though some preliminary research has shown benefits. Zinc Zinc supplements may shorten the duration of colds by up to 33% and reduce the severity of symptoms if supplementation begins within 24 hours of the onset of symptoms. Some zinc remedies directly applied to the inside of the nose have led to the loss of the sense of smell. A 2017 review did not recommend the use of zinc for the common cold for various reasons; As of 2015, there is weak evidence to support nasal irrigation with saline. There is no firm evidence that Echinacea products or garlic provide any meaningful benefit in treating or preventing colds. Vitamins C and D Vitamin C supplementation does not affect the incidence of the common cold, but may reduce its duration if taken on a regular basis. There is no conclusive evidence that vitamin D supplementation is efficacious in the prevention or treatment of respiratory tract infections. ==Prognosis==

The common cold is generally mild and self-limiting with most symptoms generally improving in a week. Severe complications, if they occur, are usually in the very old, the very young, or those who are immunosuppressed. It is estimated that sinusitis occurs in 8% and ear infection in 30% of cases. ==Epidemiology==

The common cold is the most common human disease Common cold viruses have an estimated basic reproduction number (R_0) 2–3, meaning that each infected person typically infects 2–3 others. Weather A common misconception is that one can "catch a cold" merely through prolonged exposure to cold weather. Although it is now known that colds are viral infections, the prevalence of many such viruses are indeed seasonal, occurring more frequently during cold weather. The reason for the seasonality has not been conclusively determined. Possible explanations may include cold temperature-induced changes in the respiratory system, The apparent seasonality may also be due to social factors, such as people spending more time indoors near infected people, and especially children at school. ==History==

describing the cost of the common cold While the cause of the common cold was identified in the 1950s, the disease appears to have been with humanity since its early history. The name "cold" came into use in the 16th century, due to the similarity between its symptoms and those of exposure to cold weather. In the United Kingdom, the Common Cold Unit (CCU) was set up by the Medical Research Council in 1946 and it was where the rhinovirus was discovered in 1956. In the 1970s, the CCU demonstrated that treatment with interferon during the incubation phase of rhinovirus infection protects somewhat against the disease, but no practical treatment could be developed. The unit was closed in 1989, two years after it completed research of zinc gluconate lozenges in the prevention and treatment of rhinovirus colds, the only successful treatment in the history of the unit. ==Research directions==

Antivirals have been tested for effectiveness in the common cold; as of 2009, none had been both found effective and licensed for use. The oral form of pleconaril had safety issues and an aerosol form is being studied. ==Societal impact==

The economic impact of the common cold is not well understood in much of the world. More than one-third of people who saw a doctor received an antibiotic prescription, which has implications for antibiotic resistance. ==See also==