Diphtheria is a bacterial infection caused by toxigenic Corynebacterium diphtheriae — transmitted by respiratory droplets and close contact. It causes two interlinked dangers: local disease (the pharyngeal pseudomembrane causing airway obstruction) and systemic toxin-mediated complications (myocarditis and peripheral neuropathy). Before vaccination, diphtheria killed thousands of children per year in virtually every country. DTP vaccination nearly eliminated it — but resurgence occurs wherever vaccine coverage falls.

What makes diphtheria different from a sore throat?

Diphtheria presents with: sore throat and fever; a characteristic grey-white pseudomembrane firmly adherent to the tonsils and pharynx (bleeds when removed — unlike the exudate of streptococcal tonsillitis); low-grade fever (surprisingly not very high); bull neck (massive lymphadenopathy); hoarse voice and barking cough if the membrane extends to the larynx (laryngeal diphtheria — the classic "croup"). The pseudomembrane can extend into the larynx and trachea, causing life-threatening airway obstruction. Unlike most sore throats, untreated diphtheria progresses to cardiac and neurological complications.

What are the complications of diphtheria?

Myocarditis: the most common cause of death in diphtheria — occurring in approximately 10-25% of severe cases in the second week. Presents as heart block (prolonged PR interval, bundle branch block, complete heart block), arrhythmias, cardiac failure. ECG monitoring is essential. Polyneuropathy: palatal palsy (first sign — nasal voice, regurgitation) → oculomotor paralysis (diplopia) → facial nerve palsy → peripheral motor neuropathy (weeks to months later). Airway obstruction: from membrane extension to larynx and trachea — may require intubation or tracheostomy.

Why is diphtheria resurging?

Diphtheria resurges when vaccine coverage falls below the herd immunity threshold (approximately 85-90%). Countries experiencing outbreaks have: inadequate DTP vaccination coverage; failure to maintain adult booster programmes; cold chain failures preventing effective vaccine delivery; conflict and displacement disrupting health services; and anti-vaccine sentiment. The 2021 Indonesia outbreak followed COVID-19 pandemic-related disruptions to routine immunisation programmes. Routine vaccination coverage is the primary prevention — every unvaccinated person is at risk.

Is diphtheria present in Georgia?

Georgia experienced a major diphtheria epidemic in the 1990s during the collapse of the Soviet Union — when vaccine coverage collapsed, causing thousands of cases across the former Soviet states. The epidemic was controlled by mass vaccination campaigns in the mid-1990s. Georgia has maintained high DTP coverage since then. However, C. ulcerans (from domestic animals) carrying the diphtheria toxin gene has been detected in several European countries, including potentially the Caucasus region — representing an emerging One Health concern.

How does GMJ News cover diphtheria?

GMJ News covers WHO diphtheria data, the 2021-2023 resurgence, pseudomembrane clinical recognition, antitoxin urgency, DTP vaccination and adult boosters, myocarditis and neuropathy complications, and C. ulcerans as an emerging One Health concern. Georgia's 1990s diphtheria epidemic is a powerful reminder of what happens when immunisation programmes collapse — directly relevant to PHIG's vaccination programme and Georgia's immunisation history.

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Diphtheria

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

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Diphtheria — caused by toxigenic Corynebacterium diphtheriae — produces a characteristic grey-white pharyngeal pseudomembrane and two life-threatening toxin-mediated complications (myocarditis and neuropathy) that were responsible for hundreds of thousands of deaths annually before DTP vaccination; today it causes approximately 8,000-10,000 cases and 1,000+ deaths per year globally — predominantly in under-immunised communities — with resurgence documented in Indonesia, Bangladesh, Pakistan, Yemen, Nigeria and Haiti in 2021-2023 (WHO). Diphtheria antitoxin — a horse-serum-derived antitoxin that neutralises circulating toxin — remains the only specific treatment and must be given urgently before the toxin binds irreversibly to cardiac and neural tissue.

Key messages

Vaccine-preventable — resurging in under-immunised populations

Diphtheria — once a major killer of children — is resurging in under-immunised populations: Indonesia, Bangladesh, Pakistan, Yemen, Nigeria and Haiti all reported significant outbreaks in 2021-2023. WHO declared diphtheria a public health priority requiring urgent vaccination response (WHO).

Pseudomembrane + toxin = two dangers

Diphtheria kills by two mechanisms: airway obstruction from the characteristic grey-white pharyngeal pseudomembrane (which can extend to the larynx); and toxin-mediated damage to the heart (myocarditis) and peripheral nerves (neuropathy) occurring weeks after infection.

Diphtheria antitoxin — urgency is critical

Diphtheria antitoxin (equine) is the only specific treatment — it neutralises circulating toxin but cannot reverse toxin already bound to tissues. It must be given as early as possible, before waiting for culture confirmation. WHO maintains global antitoxin stockpiles for rapid response.

DTP vaccination protects but boosters needed

The DTP (diphtheria-tetanus-pertussis) vaccine provides excellent protection. However, immunity wanes — adults need decennial boosters (Td or Tdap). The resurgence reflects vaccine coverage gaps rather than vaccine failure.

Cutaneous diphtheria — underrecognised

Cutaneous diphtheria — a non-healing skin ulcer with grey/brown membrane — is underrecognised, can occur without pharyngeal involvement, and is the form most associated with outbreaks in homeless and PWID populations.

Corynebacterium ulcerans — emerging concern

C. ulcerans (from dogs, cats and other animals) can carry the diphtheria toxin gene and cause diphtheria-like illness — an emerging One Health concern in HICs with declining C. diphtheriae immunity.

Key statistics

8-10K

diphtheria cases/year globally (WHO estimate)

WHO

5-10%

case fatality rate (higher without antitoxin or in very young/elderly)

WHO

2021-23

resurgence in Indonesia, Bangladesh, Pakistan, Yemen, Nigeria, Haiti

WHO

DTP

vaccine provides excellent protection — but boosters needed in adults

WHO

Equine

diphtheria antitoxin (DAT) — the only specific treatment

WHO EML

10yr

recommended adult Td booster interval

WHO

Diphtheria global cases reported to WHO by year — resurgence pattern

Source: WHO. After near-elimination, diphtheria resurges in settings with vaccine coverage gaps.

Glossary of key terms

Corynebacterium diphtheriae
WHOA Gram-positive, club-shaped, non-motile bacillus. Only toxigenic strains (carrying the tox gene — inserted by a bacteriophage) cause diphtheria disease. Non-toxigenic strains cause pharyngitis without the characteristic complications. Culture on selective media (Loeffler's or tellurite agar) + Elek test (toxin detection) for diagnosis.

Diphtheria toxin
WHOAn AB exotoxin — the most potent bacterial protein toxin known (after botulinum and tetanus toxins). Fragment B binds cell receptors; Fragment A inhibits protein synthesis (by ADP-ribosylation of EF-2 — elongation factor 2). Causes myocarditis (30-70% of cases), polyneuropathy (10-30%) and — in high concentrations — multi-organ failure.

Pseudomembrane
WHO/ClinicalA grey-white to grey-brown adherent membrane on the tonsils, pharynx, uvula, soft palate and (in severe cases) extending to the larynx and trachea — composed of fibrin, dead cells, red cells and bacteria. Unlike the loosely adherent membrane of streptococcal tonsillitis, the diphtheria pseudomembrane bleeds when forcibly removed. Laryngeal extension causes the characteristic hoarse voice and barking cough.

Diphtheria antitoxin (DAT)
WHO EMLEquine (horse-derived) hyperimmune serum — the only specific treatment for diphtheria. Neutralises circulating diphtheria toxin before it binds irreversibly to cardiac and neural tissue. Must be given urgently (clinical diagnosis — do not wait for culture) and before disease worsens. Risk of anaphylaxis to equine proteins — skin test and desensitisation protocol if test positive. WHO maintains a global strategic stockpile.

DTP vaccine (diphtheria toxoid)
WHO EMLDiphtheria vaccination uses diphtheria toxoid — formalin-inactivated toxin that induces antitoxin antibodies without causing disease. Three forms: DTP (full dose — children); Tdap/Td (reduced antigen dose — adult boosters). Three-dose primary series + boosters at 4-6 years and every 10 years thereafter (Td). Pregnant women recommended Tdap (protects newborn through maternal antibody transfer).

Bull neck
WHO/ClinicalMassive, tender submandibular and anterior cervical lymphadenopathy + surrounding oedema — giving the characteristic "bull neck" appearance in severe pharyngeal diphtheria. Associated with extensive membrane formation and is a marker of severe disease.