One to three days after exposure, a cold begins with sore throat, discomfort in the nose and sneezing, soon followed by a running nose and feeling unwell.
Colds are typically not associated with high fever, which should not reach more than 38.5°C. Headache, tiredness and muscle aches can occur. The watery secretions thicken during the first day and become yellow or green in colour, due to the presence of white cells.
This is the time when bacterial infection might worsen the illness. Since the lining of the upper airways is now inflamed, it is easier for normal bacteria inhabiting the surfaces to invade.
In addition, blockage of the narrow air passageways from the nose to the sinuses allows accumulation of mucous secretions in the sinuses in which bacteria can multiply. Similarly, the Eustachian tube from the throat to the middle ear can close up, leading to middle ear infection (otitis media). In children, the virus itself can cause middle ear and sinus infections.
A post-nasal drip, where infected secretions run down the back of the throat, (often causing an uncomfortable burning sensation) is not an uncommon sequel of a cold.
Laryngitis and inflammation of the trachea can be consequences of the variable extension of the viral and/or bacterial infection into the upper airways. Inflammation and swelling of the vocal cords so that they no longer move properly is what cause the loss of voice in laryngitis.
Further progression down the airways leads to bronchitis. Coughing is due to the irritation of the linings of these airways. Coughing is often worse in bed at night or on rising in the morning due to movement of secretions in response to a change in position. If other symptoms are improving, and the cough does not persist and is not productive, it is not a cause for concern.
Colds can also worsen other underlying illnesses. Chronic bronchitis due to smoking for example, can flare up with increased coughing and sputum production. It can significantly worsen the spasm of the airways in someone who has asthma, resulting in a sudden asthmatic episode.
When no complications occur, a cold should be over in four to 10 days.
Predisposing factors are not really known. Chilling the body surface does not by itself induce colds, and the ease of acquiring one does not correlate clearly with fitness, nutritional health or upper airway abnormalities (such as enlarged tonsils). However, contracting a cold virus may be facilitated by fatigue, emotional distress or allergies.
Causes of a cold
Treating a cold
Preventing a cold
Reviewed by Dr Marvin Hsiao MBBCH MMed MPH, Division of Medical Virology, Department of Clinical Laboratory Sciences, University of Cape Town. February 2015.
(Previously reviewed by Dr Eftyhia Vardas, University of the Witwatersrand 2011)