Bugs – DIPHTHERIA
Mode of Infection
Diphtheria is caused by the bacterium Corynebacterium diphtheriae. The bacteria gains access to the body through the throat via inhaled infected respiratory droplets or by contact with objects that have bacteria on them.
Most infections are asymptomatic but certain sufferers may experience symptoms. The incubation period is typically between 1 to 7 days followed by complaints of a sore and inflamed throat. Infection can be very severe, causing a raised white cell count.
A membrane forms that covers the tonsils, pharynx and the palate. It tends to be adherent and gives the appearance of a greyish green sheet across the back of an infected throat. If this membrane is removed a distinct haemorrhagic area is exposed.
Lymph glands become swollen and the patient becomes visibly toxic. Nausea and vomiting are frequently seen at this stage and the patient may also complain of the painful inablility to swallow.
The infection may spread down into the laryngeal region and cause cough, stridor and respiratory obstruction. Spontaneous healing can occur but some patients will suffer the full effect of this invasive disease with possible heart block and paralysis.
The disease is found throughout the world but is more common in regions where immunisation programmes have been limited or withdrawn due to economic reasons or from civil strife.
Humans are the only known hosts and transmission most commonly occurs by droplet or dust contamination, as the bacteria can withstand drying. The organism has also caused human infection from contaminated unpasteurised milk. Infection can also be transmitted from skin lesions such as scratches or skin abrasions. The resultant sore is usually very painful. There is usually a vesicle filled with a straw coloured fluid.
Patients with the pharyngeal form should be isolated to prevent further spread of the disease. Both Erythromycin and Penicillin are usually effective in eradicating the disease but they do not affect the acute phase of the disease. Treatment should be continued for 10 days. Patients shown to have a carrier state should also be treated.
If travellers find themselves in the midst of a diphtheria epidemic they should stay clear of public transport, cinemas, local market places and other regions where close contact with the local population is unavoidable. This is especially true during the colder times of the year.
Immunisation protects against systemic disease but does not give protection against the carriage of organisms.
All expatriates moving to live in developing countries should be offered vaccination cover.
The vaccine is a killed toxoid and is one of the recommended vaccines for childhood. In South Africa it is combined with pertussis and tetanus and given on three occasions during the first six months of life.
This gives adequate protection against diphtheria in most cases. A booster dose is then given (against all three diseases) at about 5 years of age. A second booster is recommended in adolescence or at any time in adulthood.