A common cold (coryza is the technical term) is a very common viral infection of the upper respiratory tract. One or more of several hundred different rhinoviruses may be responsible. A cold is a distinct entity from influenza, which is caused by a different group of viruses.
Colds spread from one person to another in droplets of moisture in the breath, in a cough or in a sneeze. Once inhaled, the virus settles in the nose or throat and starts multiplying rapidly. Crowds, confined spaces (e.g. buses, aircraft) and air conditioners that recycle air are renown for spreading the virus.
Most adults have a cold every year or two, usually in winter. Children, because they have not been exposed to these viruses before and so have no immunity to them, may have ten or more infections a year.
A sore throat and nose, runny and/or blocked nose, sneezing, cough, phlegm in the back of the throat, headache, intermittent fever and tiredness are the main symptoms. A secondary bacterial infection may cause pharyngitis or sinusitis.
No cure or prevention is possible. Antibiotics are not necessary as these act against bacteria, not viruses.
The symptoms can be eased by aspirin, ibuprofen or paracetamol for headache and fever, and medications for the cough, sore throat, runny nose and blocked sinuses. The more the patient rests, the faster the infection will go away.
Fewer colds are experienced by people who exercise moderately, but extreme exercise increases cold susceptibility. Colds are also caught more easily (and last longer) in smokers, those who have inadequate sleep, with stress (emotional or physical) and people who work and live alone. Those who come into contact with many different people during their daily life develop immunity to a wider range of viruses.
Many vitamin and herbal remedies are touted as cures or preventatives, but when subjected to detailed trials, none can be proved to be successful.
Colds usually last about a week, but some people have a briefer course, while in others the first cold may lower their defences so that they can catch another one, and then another, causing cold symptoms to last for many weeks.