The common cold, also known simply as a cold, is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear less than two days after exposure to the virus. These may include coughing, sore throat, runny nose, sneezing, headache, and fever. People usually recover in seven to ten days, but some symptoms may last up to three weeks. Occasionally, those with other health problems may develop pneumonia.Well over 200 virus strains are implicated in causing the common cold, with rhinoviruses, coronaviruses, adenoviruses and enteroviruses being the most common. They spread through the air during close contact with infected people or indirectly through contact with objects in the environment, followed by transfer to the mouth or nose. Risk factors include going to child care facilities, not sleeping well, and psychological stress. The symptoms are mostly due to the bodys immune response to the infection rather than to tissue destruction by the viruses themselves. The symptoms of influenza are similar to those of a cold, although usually more severe and less likely to include a runny nose.There is no vaccine for the common cold. The primary methods of prevention are hand washing; not touching the eyes, nose or mouth with unwashed hands; and staying away from sick people. Some evidence supports the use of face masks. There is also no cure, but the symptoms can be treated.
The viruses may survive for prolonged periods in the environment (over 18 hours for rhinoviruses) and can be picked up by peoples hands and subsequently carried to their eyes or nose where infection occurs. Transmission from animals is considered highly unlikely; an outbreak documented at a British scientific base on Adelaide Island after seventeen weeks of isolation was thought to have been caused by transmission from a contaminated object or an asymptomatic human carrier, rather than from the husky dogs which were also present at the base.Transmission is common in daycare and at school due to the proximity of many children with little immunity and frequently poor hygiene. These infections are then brought home to other members of the family. There is no evidence that recirculated air during commercial flight is a method of transmission. People sitting in close proximity appear to be at greater risk of infection.Rhinovirus-caused colds are most infectious during the first three days of symptoms; they are much less infectious afterwards. Weather
A common misconception is that one can "catch a cold" simply 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.