A cold – also called infectious rhinitis – is a viral infection of the nose and throat. Doctors call it a "self-limiting" condition, which means that it only lasts so long and goes away on its own.
In most people, colds are relatively harmless, but they have important social and economic impact. It is estimated that 40% of time lost from work and 30% of school absences are due to the common cold. Cold symptoms normally improve within 1 week, although some may last as long as 2 weeks.
There are over 200 different viruses responsible for causing colds. The most common type are the rhinoviruses, which cause about 40% of colds in adults. Colds occur most often from fall to early spring, when people tend to stay indoors – facilitating easy spread of these viruses.