Diphtheria is an infection of the nose and throat caused by infection with Corynebacterium diphtheriae, an anaerobic Gram-positive bacteria. Diphtheria can also affect the skin, although this is less common.
Diphtheria is a highly contagious infection that is spread through skin-to-skin contact with an infected individual or through inhaling infected particulates present in the air. When an infected person sneezes or coughs, they release millions of the bacteria into the atmosphere which remain suspended in the atmosphere inside tiny droplets of saliva.
These invisible droplets may then be breathed in through the nose or mouth by an uninfected individual. Less commonly, the bacteria is transmitted through people sharing objects such as towels, clothes or cooking utensils.
When a person is infected with the bacteria, it usually takes a few hours or days for the bacteria to multiply enough to cause symptoms. This is referred to as the incubation period. The incubation period of the respiratory form of diphtheria is usually between 2 and 5 days, with a gradual onset of disease. Children are the most commonly affected by diphtheria but adults and older individuals can also be infected.
Symptoms of the infection include:
- A high fever of 38ºC (100.4ºF) or above
- A chill
- A sore or painful throat
- A hoarse voice
- Difficulty swallowing
- Swollen lymph nodes in the neck
- Foul smelling nasal discharge
- A grey-white membrane often develops across the back of the throat and tonsils, which can obstruct breathing.
- Occasionally, diphtheria affect the skins rather than the throat. This condition leads to pus-filled skin lesions developing, usually on the hands, legs and feet. These lesions are often large, sore ulcers that leave a scar after they have healed.
- Individuals who have been vaccinated against diphtheria can still carry the infection even though they are asymptomatic for the condition. These individuals can still spread the infection to other people.
Reviewed by Sally Robertson, BSc