Diphtheria

What is Diphtheria?

Diphtheria is an acute infectious illness caused by a bacterium called corynebacterium diphtheriae (C diphtheriae). It often begins with a sore throat, after which there can be serious complications involving the heart and other organs. Thanks to immunization, the disease is now rare in Western world, but it is a growing problem in many parts of the world, so travellers in particular should be aware of the threat.

How does it occur?

Diphtheria spreads from person to person by direct contact and in germ-laden droplets in the air which form when talking, sneezing or coughing. Raw (unpasteurised) milk and inanimate objects may also spread the bacteria.

The incubation period is from one to 7 days, usually around two days. However, people can carry the disease without necessarily becoming ill.

Diphtheria has been eliminated from many developed countries but it is still common in other areas, such as Somalia and other African countries, South America, Vietnam and other parts of SE Asia, and the Indian Subcontinent. In 1990 there was an epidemic in Russia. This was poorly controlled and led to the resurgence of diphtheria in many countries of the former Soviet Union.

Why does it occur?

C diphtheriae invades the throat first, where it causes symptoms. The bacteria also produce a chemical or toxin which can spread through the blood-stream and affect more distant organs.

What are the symptoms?

The disease often starts with a sore throat, fever, headache and feeling generally unwell. The throat may not be particularly painful, but there is often a typical greyish membrane visible on one or both tonsils. Lymph nodes in the neck can be very large, giving an appearance of "bull-neck", especially in severe cases. This throat phase can last several days, and the membrane can be thick enough to obstruct breathing. Alternatively, the initial site of infection may be the nose, resulting in a bloodstained discharge from one nostril.

In the tropics, sometimes the only symptom is a skin ulcer which is very slow to heal and is covered by a tough grey membrane.

What are the complications?

Complications can set in a week or two after the initial symptoms. Involvement of the heart muscle causes low blood pressure and a variety of abnormal heart rhythms. This typically occurs 10 to 20 days after the onset of a sore throat, and it can kill, usually because of heart rate irregularities.

Diphtheria toxin can also attack the nervous system, causing paralysis of the palate (roof of the mouth) and therefore trouble speaking and swallowing. The eye muscles may also be affected. Less often, other nerves are involved, for instance those that control breathing, which can be fatal. Nerve involvement can continue to develop up to three months from the start of the illness.

What tests are done?

Swabs are taken from nose and throat (or any skin ulcers) and are sent to the laboratory to look for C diphtheriae. Basic blood tests are also done to monitor liver and kidney function.

What is the treatment?

Prompt specialist treatment is essential. Infection control is an important part of the management of diphtheria. Suspected cases are isolated, under the guidance of the local infection control team.

Injections of diphtheria anti-toxin are given to neutralise circulating toxin in the blood-stream. Anti-toxin must be given as soon as possible because it has no effect on toxin which is already bound to nerves or other tissues. Diphtheria anti-toxin originates from horses, so severe allergic reactions sometimes occur. To reduce the risk of these, a small test dose of anti-toxin is given first.

Antibiotics help eliminate the diphtheria bacteria. They are also given to close contacts of the patient.

Heart monitoring is usual. Depending on the condition of the patient, other measures may be needed, such as treatment for breathing and heart complications. These can include artificial ventilation, tracheostomy and insertion of a temporary pacemaker to regulate the heart rate.

Medications

• Diphtheria antitoxin to neutralize the diphtheria toxin.
• Antibiotics to fight remaining diphtheria germs.

Ilosone (Erythromycin)

What happens after treatment?

The traditional thinking was that survivors of diphtheria could expect a full recovery, but this is not always so and there may be long-term heart complications.

After recovery from diphtheria, the patient needs an injection of diphtheria toxoid (diphtheria vaccine, see below). This is because having the disease does not necessarily produce immunity to future infections.

How can diphtheria be prevented?

Immunisation with diphtheria toxoid gives effective protection against the disease. In the Western world, routine immunisation has almost eradicated diphtheria. The lack of a vaccination programme is one reason why the disease is widespread in certain countries.

The vaccine, diphtheria toxoid, is made from part of the diphtheria toxin. Giving it stimulates the body to produce its own diphtheria anti-toxin. The basic three-dose course of diphtheria toxoid injections is given to babies at two, three and four months of age as part of the triple vaccine. A reinforcing dose is given before school entry and again before leaving school.

Travellers to a diphtheria area should have had the full basic course of vaccine. If it has been over 10 years since the last injection, a booster of low-dose diphtheria toxoid is given before travel. The low-dose preparation is used in such cases to minimise the possibility of a reaction, which can even happen if a person is already immune to the disease. Those likely to come into contact with diphtheria should continue to have low-dose boosters at 10-year intervals.

What are the complications of immunisation against diphtheria?

Swelling and redness at the site of injection (usually the upper arm in adults) are common, as is headache, feeling unwell, and a transient fever. Serious reactions are very rare, but should be reported to the doctor if they occur.

Last updated 10 May 2016