It is a viral infection of the nose and throat (upper respiratory tract). It's usually harmless, although it might not feel that way. Many types of viruses can cause it. Healthy adults can expect to have two or three of them each year. Infants and young children may have them even more frequently. Most people recover from it in a week or 10 days. Symptoms might last longer in people who smoke. Generally, medical attention for this condition is not necessary.