The common cold is caused by a virus, and there are more than 200 viruses which cause colds. The most widely spread are the rhinoviruses, which are the cause of about one third of all colds. They affect the respiratory tract, and the infection starts in the nose, then spreads to the ears and the lungs. Once viruses enter our bodies through the nose they penetrate the cells and multiply.
The symptoms of the common cold are numerous and the most common are: sneezing, stuffy sinuses, sore throat, coughing, headache, fever, chills and general fatigue.
The duration of the common cold lasts from two days to one week, but more severe cases may last up to two weeks.
Generally, this disease has no serious complications, at most it may develop into sinusitis, especially when the cold lasts for more than 10 days without improving or getting worse. But sinusitis (sinus infection or inflammation which requires a doctor's care) only occurs in 1-5% of cases.
The common cold is an extremely contagious illness which is spread through the air and through direct contact. Viruses are spread in the air through sneezing and coughing, and are transferred from one person to another through direct contact of hands, and by touching the eyes and face. Just the smallest quantity of a cold virus is sufficient to spread the infection.
The incidence of common cold is extremely frequent in children whose immune defense mechanisms are less developed than in adults. But colds are also frequent in the aged, debilitated, and stressed people.