“Vaccination has reduced the incidence of diphtheria by more than 90%, but outbreaks can occur when vaccination efforts fall behind,” says Prof Theresa Rossouw of UP’s Department of Immunology, who offers insight into this disease, which has affected inmates at Cape Town’s Pollsmoor prison.

Recently, the Department of Health confirmed that there had been an outbreak of diphtheria at Pollsmoor Correctional Centre in Cape Town; one inmate has died. According to the National Institute for Communicable Diseases (NICD), diphtheria is a contagious and potentially life-threatening bacterial infection that manifests as either respiratory or cutaneous diphtheria.

Professor Theresa Rossouw of the Department of Immunology at the University of Pretoria (UP) and President of the South African Immunology Society unpacks the causes and symptoms of diphtheria.

What is diphtheria and what causes it?

Diphtheria is an infectious disease caused by a bacterium called Corynebacterium diphtheriae. Infection may lead to one of three conditions: infection of the airways (respiratory disease); infection of the skin (cutaneous disease); or an asymptomatic carrier state in which a person tests positive for the organism in their airways but does not have any symptoms. The word “diphtheria” comes from the Greek word for “leather’; it refers to the tough, grey membrane that covers the throat of people with respiratory diphtheria and is a distinguishing feature of the infection.

The infection is spread between people through infectious airborne droplets (such as when an infected person sneezes or coughs) or through direct contact with skin lesions. It is also possible to get diphtheria after handling an infected person’s tissues or clothes that may be contaminated with bacteria, but this is not common. 

Before vaccination became available in 1974, about one million cases occurred annually in low- and middle-income countries. Between 50 000 and 60 000 of these cases were fatal. Vaccination has reduced the incidence of diphtheria by more than 90%, but outbreaks can occur when vaccination efforts fall behind, such as during the COVID-19 pandemic. While immunised individuals can still develop clinical diphtheria, the disease occurs less frequently and is less severe.

Is diphtheria similar to COVID-19?

Yes and no. The symptoms of both diseases are very non-specific in the early stages. Patients can have a sore throat, fatigue and a low-grade fever. At this time, diphtheria can also be confused with other viral infections such as influenza, infectious mononucleosis (caused by the Epstein-Barr virus and sometimes referred to as “kissing’s” disease) and streptococcal throat infections.

But the difference becomes evident within two to three days when diphtheria progresses from mild redness of the throat and tonsils to areas of white oozing that join together to form a grey membrane that bleeds when one tries to remove it by scraping. This membrane can also form on the palate, voice box (larynx – in which case, the patient will likely have a hoarse voice) or in the nose, where patients can develop a blood-coloured, watery nasal discharge.

While patients can also have difficulty breathing, which might make it difficult to differentiate diphtheria from COVID-19, some of the common symptoms of COVID-19 – such as a dry cough, loss of taste or smell, red or irritated eyes, diarrhoea, a skin rash or discolouration of the fingers or toes – are not seen with diphtheria.

What are the five symptoms of diphtheria?

The symptoms of respiratory diphtheria usually begin two to five days after infection and may include:

• Fever and chills
• A sore throat and hoarseness, with a thick, grey membrane covering the throat and tonsils that develop after two to three days
• Swollen glands (enlarged lymph nodes) in the neck
• Difficulty breathing or rapid breathing
• Nasal discharge

Untreated diphtheria can lead to damage of the heart, nervous system and kidneys. Diphtheria of the skin presents with a painful area of redness and swelling that progress to sores or ulcers, covered by a thick grey membrane after a few days. The lesions do not heal and become chronic.  

Who is most likely to get diphtheria?

Children and adults who have not been vaccinated or are not fully vaccinated against diphtheria. Those who are in close contact of people with diphtheria may also contract it.

These could be people who live in crowded or unsanitary conditions, anyone who travels to an area where diphtheria infections are more common, and migrant and displaced populations who lack access to healthcare and vaccination.