Summary

• Colds are short-lived viral infections of the upper airways.
• Cold viruses are most commonly spread via contaminated fingers and objects.
• Typical symptoms include running nose, sneezing, headache, sore throat, cough and tiredness.
• Children get colds more often than adults do.
• Colds and influenza (flu) are different conditions, the latter being much more serious.
• Colds cannot be treated with antibiotics because they are viral infections.
• Simple personal hygiene, such as hand washing, can help prevent colds.

Description

Colds are viral infections of the nose and throat. Colds can go on to involve the sinuses, ears, larynx (vocal cords), trachea and bronchi directly or through secondary effects. The presence of the virus causes inflammation of membrane linings, so that there is swelling with obstruction (stuffiness) and increased mucous secretions. Colds are the most common type of respiratory infection; they are usually mild illnesses that naturally come to an end and only occasionally lead to further problems.

Cause

There are many viruses that can cause colds, sometimes seasonally and sometimes in epidemics. Up to 50% of colds are caused by one of the more than 100 rhinoviruses (rhino = nose). Other viruses that cause colds are the coronaviruses, adenoviruses, respiratory syncytial virus and parainfluenza viruses. Some of these viruses are capable of causing more severe disease in very young infants (such as pneumonia) but only cause colds in older children and adults.

A personwith a cold is probably contagious from 24 hours before the beginning of symptoms and then as long as thesymptoms last, usually about a week. Rhinoviruses are most often spread by direct contact with infected secretions e.g. touching objects such as handkerchiefs, door-knobs or eating utensils that a person with a cold has touched before, and then touching one's nose or mouth. Rhinoviruses are probably less often spread by airborne particles, such as when an infected person sneezes in your vicinity.

Your immune system responds by attacking the virus with white blood cells. If your immune system cannot recognise the virus from a previous infection, the response is "non-specific", meaning your body produces as many white blood cells as possible and circulates them to the infected sites. White cells produce chemicals to kill virus-infected cells, and this is what causes the nasal inflammation and swelling, increased mucous secretions, and the general feeling of achiness. Once infected with a specific cold virus, the body develops immunity to it in the form of "memory white cells" and antibodies which will control the virus quickly in the event it is encountered again. Immunity will prevent another cold being caused by the same rhinovirus for some months at least, but does not protect against others.

Symptoms

One to three days after exposure, the illness 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 causes the loss of voice in laryngitis. Further progression down the airways leads to bronchitis. Cough is due to the irritation of the linings of these airways. Cough 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 for example smoking can flare up with increased coughing and sputum production, and the spasm of the airways in asthmatics can be significantly worsened, bringing on an "asthma attack".

When no complications occur, a cold should be over in four to 10 days.

Prevalence

Colds can occur in any season and affect all people. In fact, the average person will spend two years of his or her life suffering from colds.

Children get colds far more often than adults do. This may be due to the fact that they touch their faces and noses after touching other objects a great deal, and also because they haven't been exposed to as many viruses, and had time to build up immunity, as adults have.

Risk factors

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, allergic nasal disorders or the mid-phase of the menstrual cycle.

When to see a doctor

Call a doctor if:

• An infant less than two months old develops a fever higher than 38.5°C.
• There are signs of croup (noisy and obviously difficult efforts to breathe in, barking cough) following a cold in a small child. This can lead to sudden complete obstruction of the airway.
• If there are severe coughing fits in a small child.
• If you have a persistent (more than 10 days' duration) productive cough with green, yellow, brown or rust-coloured sputum coughed up from the lungs rather than the back of the throat. Post-nasal drip (mucus running down the back of the throat from the nasal passages) can often cause a cough during a cold, and you may spit up some mucus. However, this is different to a productive cough in which the sputum is definitely coming from the lungs rather than the nasal passages, especially if this is associated with fever.
• You experience difficult or shallow breathing, or whistling noises when you breathe.
• Sinus pain persists after two to four days of home treatment, especially if nasal discharge is coloured rather than clear and you also have fever and headaches.
• A persistent nasal
discharge in the absence of cold symptoms, especially if the discharge is bloodstained.
• Ear pain lasts longer than 24 hours, or severe ear pain lasts longer than an hour.
• You have any throat pain that lasts longer than three to four days and seems different to a normal cold.

It is difficult to decide when to see a health professional for respiratory symptoms, as you may simply have a viral infection and then nothing can really help. If you have classic cold symptoms (nasal stuffiness, mild body aches, headache, and low-grade fever), treat the symptoms at home and merely watch and wait.

A cold can be distinguished from classic flu in the following ways:

• Symptoms of influenza come on more quickly and are usually more severe than those of a cold.
• Weakness, fatigue, body aches and headache are very common and often severe with classic flu; they are less common and less severe with a cold.
• Fever is very common with flu and may be up to 40ºC in adults. Chills and shaking are also common. Colds usually don't cause fever in adults, and if fever is present, it is generally low-grade.
• Severe symptoms of flu often last five to seven days. The worst of a cold is over in two to four days in most cases.
• When there have been confirmed cases of influenza in an area, symptoms of fever, muscle aches and cough are most likely to be due to flu.

Diagnosis

The diagnosis of colds is most commonly made on symptoms and signs. Fever and more severe symptoms point to influenza.

An exudate smear can be examined microscopically to exclude bacterial infections or allergic causes. It is not usually warranted, but during epidemics academic laboratories can identify specific viruses.

Treatment

Most colds will be over in seven to 10 days, and can often be treated at home. If there is mild fever and general unwellness in the early stages of a cold, bed rest is advisable. This section discusses practical methods that may alleviate cold symptoms.

The following are some practical methods that may help to alleviate cold symptoms:

• Inhale steam, with or without aromatic oils such as eucalyptus or camphor, but be very careful to avoid burns.
• Use over-the-counter cold preparations available at pharmacies. Most of these contain aspirin or paracetamol with or without codeine, and a decongestant (vasoconstrictor) such as pseudoephedrine to reduce nasal stuffiness and dry up secretions. However, a risk of the rebound phenomenon is associated with the use of decongestants: after the action of the agent is over, the secretions recur worse than before. Pseudoephedrine should not be taken if you have heart disease, high blood pressure, prostrate problems, diabetes or thyroid problems. Do not give aspirin-containing medications to children with viral infections.
• Antihistamine preparations are of little value in colds unless one has an allergic tendency ordinarily. Drowsiness may be a problematic side effect.
• Some cough preparations ease a dry, hacking cough, but a wet cough should not be suppressed, as it is important to cough up infected lung secretions.
• Mucolytics (mucus-thinning agents) such as guaifenesin can help thin nasal mucus and allow it to drain, which may help prevent secondary bacterial infections such as sinusitis.
• Antibiotics will not improve cold symptoms and will not prevent a bacterial infection from developing after a cold. However, antibiotics may be prescribed for bacterial complications such as sinusitis or otitis media.
• It has been suggested that use of vitamin C can alleviate symptoms, especially if taken early on in the course of the illness. However, no scientific evidence exists as to whether vitamin C actually fights cold viruses. Doses of 1 to 2 g a day do seem to shorten the duration and severity of colds, but certainly this is variable. Remember that continuous use of high doses can lead to kidney stones.
• If you're prone to herpes infections (cold sores), start applying aciclovir cream towards the end of the cold to the areas where you often get the sores: this might prevent cold sores from appearing; if they do appear, they will be less severe.

Prevention

There is no sure way to prevent colds, especially in children. As children grow into adults, they naturally get fewer colds.

The following may help protect you against catching colds:

• Wash your hands often, especially when you are around people with colds.
• Stop smoking. Smoking irritates the mucous membranes of the nose, sinuses, and lungs, which may make them more susceptible to infections.
• Keep your stress levels under control. If you are exposed to cold viruses, a high level of stress may increase your chances of catching a cold.
• When you have a cold, avoid sneezing without covering your mouth. Also avoid spreading nasal secretions on your hands.
• Use disposable tissues rather than a handkerchief.

Colds can't be prevented with:

• Antibiotics, which also will not prevent complications.
• Large doses of vitamin C, zinc or other vitamins and minerals.
• The flu vaccine, which only protects against the influenza virus.

(Reviewed by Dr Eftyhia Vardas, University of the Witwatersrand)

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