Diphtheria

Diphtheria is an infectious disease caused by the toxin-producing strains of the gram-positive bacillus Corynebacterium diphtheriae. This disease primarily affects the mucous membranes of the respiratory tract, although it may also affect the skin and tissue linings of the eye, ear and genital areas.

In the past, diphtheria was a leading cause of death among children, and it was once referred to as the "strangling angel of children." Fortunately, diphtheria has been largely eradication from developed countries due to comprehensive childhood vaccination programmes. (See the National Childhood Immunization Programme in Singapore).

Incubation Period:

2-5 days

Infectious Period:

Patients who contract diphteria infection may remain infectious for up to 2 - 4 weeks after the onset of illness.

Transmission:

Humans are the only known reservoir of Corynebacterium diptheriae. Infected individuals may develop symptoms of diphtheria, or they may become asymptomatic carriers.

Diphtheria is transmitted to close contacts via airborne respiratory droplets or by direct contact with nasopharyngeal secretions or skin lesion exudates. Overcrowding and poor living conditions can further contribute to the spread of diphtheria.

Signs & Symptoms:

Presentation generally depends on the site of infection. There may be symptoms of local infection, as well as symptoms as a result of the spread of potent diphtheria toxin.

1. Respiratory Diphtheria
Symptoms of respiratory diphtheria may include fever, malaise, sore throat, hoarseness of voice, barking cough etc. With the progression of respiratory diphtheria, patients may also develop an adherent gray membrane (known as a "pseudomembrane") forming over the lining tissues of the tonsils and/or nasopharynx. There may also be swelling of the cervical lymph nodes and swelling of neck, resulting in a "bull neck" appearance. Further spread of the inflammation into the larynx and trachea can cause airway obstruction and potentially lead to suffocation and death.

2. Cutaneous Diphtheria
Cutaneous diphtheria is characterized by a non-healing skin ulcer covered by a dirty gray membrane. It tends to remain a localized infection that is rarely associated with systemic spread. It also tends to induce a brisk antibody response and is therefore immunizing.

3. Systemic Disease
Dissemination of diphtheria toxin can also lead to systemic disease, causing complications such as myocarditis, endocarditis, and neurologic problems such as paralysis of the soft palate, vision problems, and muscle weakness.

Diagnosis:

The diagnosis of diphtheria is confirmed by isolation of the bacterium Corynebacterium diphtheriae from nose, throat and skin lesion cultures. Nose and throat cultures are also taken from close contacts.

Doctors also test the patient's antibody levels to diphtheria toxin to help ascertain the probability of the diagnosis of diphtheria as well as the potential for severe illness.

Other tests, such as ECG (to detect conduction blocks), imaging studies, and blood tests can also help assess the extent of involvement of the disease.

Management:

Diphtheria antitoxin is the mainstay of therapy, and it should be administered without delay, as its effectiveness is greatest if it is administered early in the course of the disease. It neutralizes circulating diphtheria toxin and reduces the progression of the disease. Antitoxin is not recommended for asymptomatic carriers and it is usually of no value in cutaneous diphtheria.

Antibiotics should also be administered as soon as possible to patients with suspected diphtheria. Antibiotics eradicate the bacteria, thereby stopping toxin production. Asymptomatic carriers and close contacts also require treatment with antibiotics.

Patients should also be given diphtheria toxoid immunization since infection does not confer immunity.

Prevention & Control:
• Isolation of suspected cases to prevent further spread.

• Routine childhood vaccination.

• Travelers to diphtheria endemic countries should review and update their vaccinations as necessary.

The article above is meant to provide general information and does not replace a doctor's consultation.
Please see your doctor for professional advice.