Diphtheria

Diphtheria is a toxin-mediated infection caused mainly by toxigenic *Corynebacterium diphtheriae* strains, with occasional disease due to toxigenic *C. ulcerans* and *C. pseudotuberculosis* ^[1]. The clinical syndrome is typically an acute respiratory infection, and its defining local lesion is a pseudomembrane in the throat ^[1]. Source-backed detail on other defining phenotypes is not yet available beyond the acknowledgment that cutaneous infection may occur ^[1].

The illness is generally acute and respiratory, with formation of a throat pseudomembrane as a characteristic feature ^[1]. Cutaneous diphtheria is also described, indicating that disease expression is not limited to the airway ^[1]. Systemic manifestations such as myocarditis and neuropathy are attributed to diphtheria toxin and are associated with increased fatality risk ^[1]. The toxin inhibits protein synthesis and causes cell death, providing the mechanistic basis for severe disease ^[1]. Source-backed detail on symptom timing, full clinical progression, or other complications is not yet available ^[1][2].

Diphtheria was once a major cause of childhood morbidity and mortality, but it declined markedly after introduction of vaccine ^[2]. The disease can re-emerge when recommended vaccination programmes are not sustained, and recent outbreaks have been linked to civil unrest that interrupts vaccination and healthcare access ^[2]. Thousands of cases are still reported annually from several countries in Asia and Africa, along with many outbreaks, and changes in the epidemiology have been reported worldwide ^[1]. Source-backed detail on population-specific incidence patterns beyond these broad observations is not yet available ^[1][2].

The available sources indicate that vaccination does not fully prevent colonization or transmission, because vaccinated individuals can still become colonized and transmit infection ^[2]. Untreated cases may remain colonized for a median of 18.5 days, and most clear *Corynebacterium diphtheriae* within 48 days ^[2]. Asymptomatic carriers are less efficient transmitters than symptomatic cases, causing 76% fewer cases over the course of infection ^[2]. Source-backed detail on the exact route or exposure mechanism is not yet available from the provided material ^[2].

The sources identify populations at elevated risk in broad terms rather than by a detailed clinical list: communities where recommended vaccination programmes are not sustained, settings affected by civil unrest that interrupts vaccination and healthcare access, and adults who are becoming increasingly susceptible are all noted ^[2]. Outbreak settings are especially important because vaccination alone may not interrupt transmission ^[2]. Source-backed detail on age-, comorbidity-, or occupation-specific risk groups is not yet available ^[1][2].

Effective vaccines are available, and receipt of 3 doses of diphtheria toxoid vaccine was estimated to be 87% effective against symptomatic disease and to reduce transmission by 60% ^[2]. However, vaccination alone can interrupt transmission in only 28% of outbreak settings, so isolation and antibiotics are described as essential measures for control ^[2]. The literature also emphasizes that sustained vaccination programmes and healthcare access are important to prevent re-emergence ^[2]. Source-backed detail on specific schedules, boosters, or additional exposure-control measures is not yet available ^[2].

In surveillance terms, diphtheria should be read as a toxin-mediated infection with outbreak potential in settings where vaccination coverage or healthcare access is disrupted ^[2]. Public-health interpretation should account for the fact that vaccinated people may still be colonized and transmit, so case finding must consider symptomatic illness as well as carrier states ^[2]. Because systemic toxin-mediated complications are linked to increased fatality risk, reports with myocarditis or neuropathy merit careful epidemiologic attention ^[1]. Source-backed detail on formal notification thresholds or laboratory algorithms is not yet available, beyond the statement that clinical diagnosis is confirmed by isolation and identification of the causative *Corynebacterium* spp. ^[1].

1. 1 Sharma NC et al. Diphtheria. Nat Rev Dis Primers. 2019 Dec 5. PMID: 31804499. doi: 10.1038/s41572-019-0131-y. PubMed: https://pubmed.ncbi.nlm.nih.gov/31804499/
2. 2 Truelove SA et al. Clinical and Epidemiological Aspects of Diphtheria: A Systematic Review and Pooled Analysis. Clin Infect Dis. 2020 Jun 24. PMID: 31425581. doi: 10.1093/cid/ciz808. PubMed: https://pubmed.ncbi.nlm.nih.gov/31425581/
3. 3 Gidengil C et al. Safety of vaccines used for routine immunization in the United States: An updated systematic review and meta-analysis. Vaccine. 2021 Jun 23. PMID: 34049735. doi: 10.1016/j.vaccine.2021.03.079. PubMed: https://pubmed.ncbi.nlm.nih.gov/34049735/
4. 4 Diphtheria and Pseudo-Diphtheria. The Journal of Laryngology, Rhinology, and Otology. 1894. doi: 10.1017/s1755146300155519. DOI: https://doi.org/10.1017/s1755146300155519
5. 5 Diphtheria and Diphtheria Carriers. BMJ. 1943. doi: 10.1136/bmj.1.4288.332-c. DOI: https://doi.org/10.1136/bmj.1.4288.332-c
6. 6 DIPHTHERIA AND PSEUDO-DIPHTHERIA. The Lancet. 1896. doi: 10.1016/s0140-6736(02)00253-2. DOI: https://doi.org/10.1016/s0140-6736(02)00253-2

ICD-10

A36

ICD-11

1C15

Total cases

2K

Total deaths

9

Peak month

2026-05

Coverage

7 reporting countries · 2000-01-01 → 2026-06-01