The common cold, also known as a viral upper respiratory tract infection.
More than 200 different types of viruses are known to cause the common cold. Because so many different viruses can cause a cold and new cold viruses constantly develop, the body never builds up resistance against all of them. Colds are a frequent and recurring problem.
MODE OF SPREAD
The common cold is usually spread by direct hand-to-hand contact with infected secretions .Colds are most contagious during the first 2 to 4 days after symptoms appear, and may be contagious for up to 3 weeks. Your can catch a cold from person-to-person contact or by breathing in virus particles spread through the air by sneezing or coughing. Touching the mouth or nose after touching skin or another surface contaminated with a virus can also spread a cold.