Progression
A cold usually begins with fatigue, a feeling of being chilled, sneezing, and a headache, followed in a couple of days by a runny nose and cough. Symptoms may begin within sixteen hours of exposure and typically peak two to four days after onset. They usually resolve in seven to ten days, but some can last for up to three weeks. The average duration of cough is eighteen days and in some cases people develop a post-viral cough which can linger after the infection is gone. In children, the cough lasts for more than ten days in 35–40% of cases and continues for more than 25 days in 10%. Causes
Viruses
The common cold is an infection of the upper respiratory tract which can be caused by many different viruses. The most commonly implicated is a rhinovirus (30–80%), a type of picornavirus with 99 known serotypes. Other commonly implicated viruses include human coronaviruses (≈ 15%), influenza viruses (10–15%), adenoviruses (5%), human respiratory syncytial virus (RSV), enteroviruses other than rhinoviruses, human parainfluenza viruses, and human metapneumovirus. Frequently more than one virus is present. In total, more than 200 viral types are associated with colds. Transmission
The common cold virus is typically transmitted via airborne droplets (aerosols), direct contact with infected nasal secretions, or fomites (contaminated objects). Which of these routes is of primary importance has not been determined.
Cough medicines are not recommended for use in children due to a lack of evidence supporting effectiveness and the potential for harm. In 2009, Canada restricted the use of over-the-counter cough and cold medication in children six years and under due to concerns regarding risks and unproven benefits. The misuse of dextromethorphan (an over-the-counter cough medicine) has led to its ban in a number of countries. Intranasal corticosteroids have not been found to be useful.In adults short term use of nasal decongestants may have a small benefit. Antihistamines may improve symptoms in the first day or two; however, there is no longer-term benefit and they have adverse effects such as drowsiness. Other decongestants such as pseudoephedrine appear effective in adults. Combined oral analgesics, antihistaminics and decongestants are generally effective for older children and adults. Ipratropium nasal spray may reduce the symptoms of a runny nose but has little effect on stuffiness. Ipratropium may also help with cough in adults. The safety and effectiveness of nasal decongestant use in children is unclear.Due to lack of studies, it is not known whether increased fluid intake improves symptoms or shortens respiratory illness. As of 2017 heated and humidified air, such as via RhinoTherm, is of unclear benefit. One study has found chest vapor rub to provide some relief of nocturnal cough, congestion, and sleep difficulty.Some advise to avoid physical exercise if there are symptoms such as fever, widespread muscle aches or fatigue.