Introduction – Diphtheria
Diphtheria is a acute serious infection caused by bacteria called Corynebacterium diphtheriae, gram-positive bacillus. Diphtheria is acute bacterial infection is an endemic disease.
Diphtheria toxin is an exotoxin secreted by Corynebacterium diphtheria that may cause diphtheria. Bacilli multiply locally in throat and produce exotoxin. It is childhood disease, affect children younger than 5 years old.
Types of Diphtheria
1. Pharyngotonsillar diphtheria
2. Laryngotracheal diphtheria
3. Nasal diphtheria – affects the mucous membranes of nose
4. Cutaneous diphtheria
Epidemiological Triad
Agent – The causative organism is cornybacterium diphtheriae and the source of infection are cases and carrier.
Cases – subclinical to clinical, subclinical disease has no recognizable clinical findings. In clinical disease has signs and symptoms that can be recognized.
Carrier – person in whom organisms are present and may be multiplying, but shows no clinical response to their presence.
The causative organism is present in nasopharyngeal secretions, discharge of skin lesions, contaminated fomites.
The period of infectivity is from 14 to 28 days from the onset of diseases, in cases and carriers it remains infective for a prolonged period.
Host – Diphtheria affects children of 1 to 5 years of age.
It affects both the sexes.
Environmental factors – Diphtheria is common in winter although it occurs in all season.
Mode of Transmission
Portal of entry – Respiratory route, skin cuts, wounds
1. Droplet nuclei
2. Infected cutaneous lesion
3. Infective object or dust, contaminated with nasopharyngeal secretions.
4. Spread from person to person contact through respiratory droplets from coughing or sneezing or talking.
5. Touching infected open sores or wound or ulcers.
Incubation Period
The incubation period of diphtheria is 2-5 days with a range of 1 to 10 days.
Pathophysiology of Diphtheria
1. Cornybacterium diphtheria
2. Bacilli lodged and multiply locally in the throat or tonsil or nasopharynx and secrete exotoxin
3. Produce local and systemic symptoms
4. Lead to necrosis of epithelial cells and forms grayish white Pseudo membrane
5. Produce Pharyngitis and Cutaneous lesion
Clinical Manifestation
Respiratory Diphtheria
1. Pharyngotonsillar diphtheria, characterized by-
1. Sore throat
2. Difficulty in swallowing
3. Low grade fever, Mild fever
4. Weakness
5. Swollen glands in the neck
In early stages – a whitish membrane appear that can be wiped off easily. Later it becomes thick, and turn blue-white to grey black and is adherent to surface. It is difficult to remove and if trying to remove result in bleeding.
Mucosal erythema around the membrane developed and lead to edema of submandibular area and bull neck appearance.
2. Laryngotracheal diphtheria
It is associated with pharyngotonsillar diphtheria, sign and symptoms are-
1. Hoarseness of voice (abnormal change in voice)
2. Croupy cough (upper airway infection obstructs breathing and causes a barking cough)
Diphtheria Skin Infection
The bacteria can infect the skin, causing open sores, wound,s or ulcers.
Lab Investigation
1. Swab taken from nose and throat
2. Schick test – Intradermal Test
Test – Presence of antitoxin (immunity status) and state of hypersensitivity to diphtheria toxin.
In schick test toxin 0.2ml is injected intradermally into the fore arm as test arm while into opposite arm i.e, control arm, same amount of inactivated toxin (inactivated by heat) is injected intradermally.
Following types of reactions can be seen –
1. Negative reaction – if the person is immune, no reaction of any kind.
2. Positive reaction – within 24-36 hours, appears red flash of 10-15 diameter and later on slowly fades into a brown patch.
Control arm- no change occur
The person susceptible to diphtheria
3. Pseudo positive reaction – a red flush develops equally in both arm .
Test arm – a red flash of a size less than true positive reaction.
Control arm – a red flash of a size less than positive reaction.
The reaction fades and disappears from both arms by 4th day.
It is an allergic type reaction.
4. Combined reaction –
Test arm- true positive reaction is seen on test arm.
Control arm – Pseudopositive reaction is seen on control arm
The person is susceptible to diphtheria
Prevention of Diphtheria
1. Cases – Diphtheria antitoxin administered I/V or I/M depending upon severity of care.
2. Carriers – carriers should be given oral erythromycin for 10 days.
3. Contacts – The individuals who come in contact with cases should be treated depending upon their immunisation status.
1. Those who were immunised within 2 years of exposure to case – as the individuals have received primary immunisation or booster dose within previous 2 year. So no further action is required.
2. Those who were immunised for more than 2 years – only booster dose of diphtheria toxoid is given to individuals.
3. Those who were not immunised at all; they require –
1. Prophylactic treatment i.e penicillin or erythromycin
2. Diphtheria AntItoxins
3. Active immunisation – Diphtheria (D) vaccine is a toxoid (inactivated toxin) that is administered to infants and young children combined with tetanus toxoid (T).
4. Immunization
a. Combined vaccines – DPT, DT
Vaccines is the best way to prevent diphtheria. DPT; Diptheria, pertussis (whooping cough), and Tetanus
Age Vaccine Dose Route
6 weeks DPT-1 0.5ml deep I/M
10 weeks DPT-11 0.5ml deep I/M
14 weeks DPT-11 1 0.5ml deep I/M
1-2 years DPT(booster dose-1) 0.5ml deep I/M
5yrs to 6yrs DPT (booster dose-11) 0.5ml deep I/M
b. Single vaccines
Single vaccines – FT (Formal toxoid) – APT (Alum precipitated toxoid) – PTAP (Purified toxoid aluminium phosphate) – PTAH (Purified toxoid aluminium hydroxide)
5. Antisera – Diphtheria Antitoxins
For the treatment of diphtheria, diphtheria toxins prepared from horse serum is given.
Antisera Purpose Route
Diphtheria prophylactic S/C or I/M
Antitoxins therapeutic I/M , I/V
Control of Diphtheria
1. Early detection of cases and carries – detection of cases and carries can control the source of infection. The detected of cases is done by taking swabs from nose and throat and is examined by cultural methods for diphtheria bacilli.
2. Isolation
3. Treatment of cases and carriers
Complication of Diphtheria
1. Breathing problems
2. Heart damage – myocarditis
3. Polyneuropathy – Nerve damage
4. Loss of the ability to move (paralysis)
FAQ on Diphtheria
1. Who is most at risk for diphtheria?
Increased risk of contracting diphtheria, children under 5 years and adults over 60 years old, children and adults who don’t receive their vaccinations, people residing in crowded or unsanitary conditions. Peron travels to a diphtheria-infected area where diphtheria infections are more common.
2. How does diphtheria spread from one person to another?
Diphtheria is an infection caused by strains of Corynebacterium diphtheriae bacteria that make toxin. Diphtheria infection spreads from person to person through respiratory droplets from of coughing or sneezing. It can also transmit by touching open sores or ulcers with a diphtheria skin infection person.
3. What is black diphtheria?
Black diphtheria when throat infection causes a gray to black, tough, fiber-like covering, which can obstruct or block airways. Diphtheria can infects the skin first and causes skin lesions. Once people are infected, bacteria make dangerous substances called toxins.
4. What are the types of diphtheria?
There are four types of diphtheria –
1. Classical respiratory diphtheria
2. Laryngeal diphtheria
3. Nasal diphtheria and
4. Cutaneous diphtheria (skin lesions)
