Define Diphtheria :

Definition : Diphtheria is an acute bacterial disease caused by toxigenic strains of Corynebacterium diphtheria (and occasionally ulcerans) and characterized in its typical form by the presence of membrane (pseudomembrane) in the throat and generalized toxaemia.

Symptoms of diptheria :

1. A sore throat and hoarseness.
2. Painful swallowing.
3. Swollen glands (enlarged lymph nodes).
4. A thick, gray membrane covering your throat and tonsils.
5. Difficulty breathing or rapid breathing.
6. Nasal discharge.
7. Fever and chills.
8. Malaise.

Types of diphtheria:

Three major clinical types have been described : 

• Anterior nasal
• Tonsillar (faucal).
• Pharyngeal.

There may be other clinical types, e.g. Laryngeal and cutaneous diphtheria. It occasionally involves the other sites such as eyes (conjunctiva), nose or vagina.

Laryngeal diphtheria is serious in infants and young children, while nasal diphtheria is mild and often chronic.

Case definition of diphtheria:

A respiratory tract illness characterized by :

• Sore throat (laryngitis, pharyngitis or tonsillitis), and
• Fever and
• Adherent membrane of the tonsils, pharynx and or nose, and
• Without other apparent cause determined by the physician.

Pathogenesis of diphtheria :

Pathogenesis of diptheria : The bacilli multiply locally, usually in the throat, and elaborate a powerful exotoxin, which is responsible for : 

• The formation of a grayish/yellowish membrane (false membrane) commonly over the tonsils. pharynx, or larynx (or at the site of implantation) with well-defined edges and the membrane cannot be wiped away.
• Marked congestion, oedema or local tissue destruction.
• Enlargement of regional lymph nodes and
• Signs and symptoms of toxaemia.

Investigations of diptheria :

1. Gram stains or throat culture to identify the diphtheria bacteria.
2. Toxin assay (to detect the presence of the toxin made by the bacteria).
3. Electrocardiogram (ECG).

Clinical diagnosis of diphtheria : 

Clinical diagnosis of diphtheria which should forms the basis for starting Immediate treatment on observation of a whitish membrane, especially if extending to the uvula and soft palate.

Treatment of diphtheria :

1. Notification : clinical diagnosis of diphtheria must be notified to the public health authorities.
2. Isolation : The patient must be sent urgently to a specialist infectious diseases unit and managed in strict isolation attended by staff with a clearly documented immunization history until three swabs 24 hours apart are culture-negative
3. Diphtheria antitoxin : To be injected intramuscularly. A careful history of previous horse serum injections or allergic reactions should be taken and a small test injection of serum should be given half an hour before the full dose in every patient. For disease of moderate severity, 16,000 40,000 IU i.m will suffice, and for mild cases 4000 8000 U.
4. Anti bacterial:

• Penicillin (1200 mg 6 hourly iv) or amoxicillin (500 mg 8 hourly) should be administered for 2 weeks to eliminate C diphtheriae.
• Patients allergic to penicillin can be given Erythromycin.

   5. Immunization : Due to poor immunogenicity of primary infection all sufferers should be immunized with diphtheria toxoid following recovery.

   6.Treatment of complications.

Epidemiology of diphtheria :

A. Occurrence : Diphtheria occurs worldwide. Its incidence in the West has fallen dramatically following widespread active immunization.

B. Ecological triad :

1. Agent: Corynebacterium diphtheriae is a gram positive bacterium.

2. Host factors :

• Age: 1 to 5 years mainly.
• Sex: Both sexes are affected.
• Immunity: Infants are immune for 6 weeks after birth.

3. Environmental factors : Occur in all seasons, in winter maximum incidence is reported.

C. Natural history :

1. Source of infection :

• Clinical cases
• Carriers.

2. Infective materials :

• Nasopharyngeal secretions.
• Discharge from skin leisions.
• Contaminated fomites.
• Infective dust.

3. Infectious period: 14-28 days from the onset of the disease.

4. Mode of transmission :

• Mainly by droplet infection. 
• From infected cutaneous lesion.

5. Incubation period : 2-6 days.

Complications of diphtheria. 

1st week : Laryngeal obstruction or paralysis.

2nd week :

• Myocarditis.
• Acute circulatory failure (due to myocarditis, occurs around the 10th day).

3rd week :

• Peripheral neuropathy
• Palatal paralysis.

4th week: Paralysis of eye muscles of accommodation (manifest by difficulty in reading small point).

5th week :

• Generalized polyneuritis & weakness.
• Paresthesia.

6th week :

• Pharyngeal paralysis.
• Diaphragmatic paralysis.

Control & prevention of diphtheria :

1. Active immunization against diphtheria : DPT or DT toxoid may be used. Protection conferred by the primary series of 3 doses is excellent. A booster dose one year after the primary be considered.
2. Active search for cases and carriers amongst the contacts.
3.  Isolation:  All cases and carriers to be isolated till the throat swabs (2 swabs taken 24 hours apart) are negative.
4. Disinfection : Concurrent disinfection of all articles in contact with patient and all articles soiled by discharges of patient.
5. Treatment :

• Antitoxin.
• Penicillin.