Diphtheria is an infection caused by a bacterium called Corynebacterium diphtheriae. It is mainly spread by droplets expelled from the nose and mouth by coughing and sneezing. The infection may cause the lining of the throat to swell forming "a false membrane" which can cause difficulties in breathing or swallowing. The bacterium produces a poison or toxin which can seriously damage the heart muscle, adrenal tissue, and the nervous system. Depending on the severity of the case, the pre-existing level of immunity and the speed with which treatment is started the patient may die. Five to ten per cent of cases are fatal.
The incubation period is from two to five days. Patients with untreated disease may be infectious for up to four weeks, but carriers of the disease may potentially transmit the infection for longer.
Who is at risk in Europe?
Individuals who have not been vaccinated (especially if they travel to countries where diphtheria is still common) are at risk. Approximately half of UK adults over 30 years of age are vulnerable to diphtheria; this proportion increases to over 70% in older age cohorts.
Diphtheria cases continue to be reported in South-East Asia, South America, Africa and India. Most cases of diphtheria that have occurred in recent years in the UK have been imported from the Indian subcontinent or from Africa.
With increased international travel there is always the threat that foreign strains of a disease could be introduced into the country. Given the likely numbers of individuals who may not have high levels of circulating antibodies it is important to maintain high levels of protection so that the disease cannot take hold.
Diphtheria is a serious disease which can be prevented by vaccination. In the UK vaccination against diphtheria infection is included in the childhood immunisation schedule as part of a combined vaccine. The first dose is given to babies at 2 months old followed by two additional doses at one month intervals. A booster dose is given three years after completion of the primary course (pre-school booster) and another booster given ten years after the first, usually at age 13-18 years.