Causes of Cold Colds are caused by rhinoviruses. Since it is spread by the respiratory route the risk is highest in crowded places and in places when there is prolonged contact, as in play groups or day care centers. Risks of Cold Colds are highly contagious. Someone with a cold can easily pass it onto others. The cold virus is spread via air particles that are expelled when coughing or sneezing. It is also spread when someone with a cold rubs their eyes or nose and then touches another object before washing their hands and someone else comes in contact with such objects later, such as a phone or door knob.