Diphtheria is a serious bacterial infection that affects the nose, throat and sometimes, the skin of an individual. It is caused by the bacterium Corynebacterium species, mainly by toxin-producing Corynebacterium diphtheriae and rarely by toxin-producing strains of C. ulcerans and C. pseudotuberculosis. It manifests as laryngitis, pharyngitis or tonsillitis and is associated with the presence of an adherent membrane covering the tonsils, pharynx and/or nose. Beyond the respiratory symptoms, approximately a quarter of cases may develop heart problems (myocarditis). The mainstay of Diphtheria treatment is antibiotics and Diphtheria antitoxin (DAT).

Over the past five decades, the incidence of diphtheria has reduced dramatically worldwide because of widespread immunisation using a diphtheria toxoid-containing vaccine. The number of Diphtheria cases reported to the World Health Organization (WHO) declined from about 100,000 cases in 1980 to less than 10,000 cases in 2021. However, in recent years, there has been a gradual rise in cases with over 20,000 cases recorded in 2019. Diphtheria is primarily controlled by the prevention of infection through high population immunity achieved by high vaccination coverage. Consequently, Diphtheria outbreaks reflect inadequate vaccination coverage.

In Nigeria, there was an outbreak in Borno, north-eastern Nigeria in 2011 with a total of 98 cases, and 21 deaths (case fatality ratio was 21.4%). This outbreak and the associated high case fatality were due to a combination of low vaccination coverage, delayed clinical recognition and laboratory confirmation, and the absence of antitoxin and antibiotics for treatment.

Case Definitions

Suspected case: Any person with an illness of the upper respiratory tract characterized by the following: pharyngitis, nasopharyngitis, tonsillitis or laryngitis AND adherent pseudo-membrane of the pharynx, tonsils, larynx and/or nose.

Laboratory confirmed case: A person with Corynebacterium spp. isolated by culture and positive for toxin production, regardless of symptoms.

Diphtheria spreads easily between people by direct contact or through the air through respiratory droplets from coughing or sneezing. It may also be spread by contaminated clothing and objects. A person is infectious for as long as the bacteria are present in respiratory secretions, usually two weeks without treatment, and seldom more than six weeks.

In rare cases, chronic carriers may spread the bacteria for six months or more

The most common type of diphtheria is classic respiratory diphtheria. The onset of signs and symptoms is usually from 2 – 5 days (could be as high as 10 days) after exposure. Initial symptoms may be mild and include fever, runny nose, sore throat, cough, and red eyes (conjunctivitis). In severe cases, the bacteria produce an exotoxin that causes a thick grey or white patch (pseudo-membrane) on the tonsils and/or at the back of the throat. This can block the airway making it hard to breathe or swallow and causing a barking cough. The neck may swell in part due to enlarged lymph nodes and may frequently confer a bull-neck appearance.

The exotoxin produced by the bacteria may also enter the bloodstream causing complications such as inflammation and damage of the heart muscle, inflammation of nerves, kidney problems, and bleeding problems due to decreased blood platelet count. The damaged heart muscles may result in an abnormal heart rate and inflammation of the nerves may result in paralysis. The infection can also affect the skin (cutaneous diphtheria). More rarely, it can affect mucous membranes at other non-respiratory sites, such as the genitalia and conjunctiva.

Complications due to diphtheria usually occur in the second and third week following infection. This includes corneal scarring (aggravated by vitamin A deficiency), encephalitis (more common in older children and adults, 0.1%), diarrhoea, pneumonia (a major cause of death) and subacute sclerosing panencephalitis (rare, delayed complication; associated personality changes, seizures, motor disability, progressing to coma and death). Case fatality ratios up to 10% have been reported in diphtheria outbreaks and are higher in settings where diphtheria antitoxin (DAT) is unavailable.

The most reliable method of confirming diphtheria is by the culture of the organism from any of the specimens mentioned above and by demonstrating toxin production using an immunoprecipitation reaction (the modified Elek test). PCR can be done directly on swab material to detect the presence of the A and B subunits of the diphtheria toxin gene (tox).

However, in some cases the presence of tox does not confirm the production of toxin; positive PCR results should therefore always be confirmed with the Elek test if there is an isolate

Diphtheria infection is treated with the administration of a diphtheria antitoxin (DAT), administered intravenously or through an intramuscular injection. Antibiotics can also be given to eliminate the bacteria to prevent transmission and toxin production to others.

Close contacts of the patient are to be monitored for signs and symptoms for 10 days from the last contact with a suspected case.

Healthcare workers exposed to the case’s oral or respiratory secretions or exposed to their wounds should also be monitored. Prophylactic antibiotics (penicillin or erythromycin) are indicated for close contact for seven days.

Prevention

Parents should ensure that their children are fully vaccinated against diphtheria with three (3) doses of the pentavalent vaccine as recommended in the childhood immunisation schedule. The Nigeria childhood immunisation schedule recommends three (3) doses of pentavalent vaccine (diphtheria toxoid-containing vaccine) are recommended for children in the 6th-, 10th- and 14th -week of life. WHO recommends a 3-dose series of diphtheria toxoid-containing vaccines in the first year of life beginning at 6 weeks of age and advises that 3 booster doses of diphtheria toxoid-containing vaccine are provided during childhood and adolescence to ensure long-term protection.

Individuals with signs and symptoms suggestive of diphtheria should isolate and take precautionary measures while visiting the healthcare facility for diagnosis and treatment

Close contacts with a confirmed case of diphtheria should be closely monitored given antibiotics prophylaxis and started on diphtheria antitoxin treatment when indicated.

Healthcare workers should maintain a high index of suspicion for diphtheria i.e., be vigilant and look out for symptoms of diphtheria.

Healthcare workers should practice standard precautions always while handling patients and body fluids i.e., always wear Personal Protective Equipment (PPE) irrespective of the patient’s provisional diagnosis.

In endemic settings and outbreaks, healthcare workers may be at greater risk of diphtheria than the general population. Consequently, special attention should be paid to immunizing healthcare workers (doctors, nurses, laboratory scientists, support staff etc) who may have occupational exposure to Corynebacterium diphtheriae.

Diphtheria is one of the priority diseases in Nigeria requiring immediate reporting and as such all suspected cases of diphtheria picked by healthcare workers in a health facility are required to be reported to the respective Local Government Area (LGA) Disease Surveillance and Notification Officer (DSNO) either directly or through the health facility surveillance focal person depending on what is obtainable within the health facility. Reports from the health facility are expected to reach the LGA DSNO within 24 hours. The LGA DSNO in turn reports the case to the state epidemiologist who then reports to NCDC.