Diphtheria
Diphtheria is a widespread severe infectious disease caused by the bacterium Corynebacterium diphtheriae and the toxin they produce. It is a potentially life-threatening, vaccine-preventable disease that primarily affects the throat and upper airways and has the potential for epidemics (WHO, 2024a).
Primary reference(s)
WHO, 2024a. Diphtheria. World Health Organization (WHO). Accessed 16 February 2024.
Annotations
Additional scientific description
Diphtheria is a vaccine-preventable disease caused by toxin-producing Corynebacterium species. Diphtheria outbreaks in human populations are primarily caused by Corynebacterium diphtheriae, which is spread from person to person, usually through respiratory droplets, secretions or infected skin lesions. Diphtheria may also be caused by C. ulcerans or C. pseudotuberculosis; however, because these are zoonotic infections, with limited person-to-person transmission, they are rarely associated with large outbreaks (WHO, 2024a; WHO, 2024b).
Typical diphtheria cases present with upper respiratory tract symptoms including pharyngitis, nasopharyngitis, tonsillitis or laryngitis, or any combination of these symptoms. The toxin produced by the bacterium can cause the formation of a pseudo membrane in the upper respiratory tract and may damage other organs. Severe complications include acute respiratory obstruction, acute systemic toxicity, myocarditis, renal failure, neurologic complications and death. Case fatality rates (CFR) above 10% have been reported in diphtheria outbreaks; with higher CFRs appearing in settings where appropriate treatment options, such as diphtheria antitoxin [DAT], is limited (WHO, 2024b).
Following the establishment of the Expanded Programme on Immunization (EPI) in 1974, which included a childhood multivalent vaccine (including diphtheria toxoid), the global incidence of diphtheria decreased dramatically. However, dramatic resurgences of the disease have been seen globally over the past decade, with an average of almost 10,000 cases reported annually - a 50% increase on the decade prior. Although most outbreaks have been small and sporadic, larger outbreaks have occurred in areas of low vaccine coverage or in fragile, conflict-affected settings including Bangladesh, Ethiopia, Haiti, India, Indonesia, Venezuela (Bolivarian Republic of) and Yemen; one of the largest outbreaks of the decade began in 2022 in Nigeria and is still ongoing (WHO, 2024b).
Culture and identification of C. diphtheriae, followed by confirmation of toxin production by Elek testing, remains the gold standard of laboratory confirmation for diphtheria. However, methods including automated identification systems, molecular testing and genotyping can also play a role in informing public health decisions, sometimes more quickly and effectively than standard methods in an outbreak setting. Careful consideration of the benefits and limitations of each method is required to ensure the best use of available resources and alignment with public health goals (WHO, 2024b).
The World Health Organization has published interim guidance for clinical management and laboratory diagnosis of diphtheria (WHO, 2024a; 2024b).
Metrics and numeric limits
In 2023, there were 24,780 reported cases of diphtheria globally (WHO, 2025).
In 2023, an estimated 84% of children worldwide received the recommended 3 doses of diphtheria-containing vaccine during infancy (WHO, 2024a).
Key relevant UN convention / multilateral treaty
International Health Regulations (2005), 3rd ed. (WHO, 2016).
Drivers
Diphtheria has seen resurgences any time immunization coverage becomes low. Damaged health infrastructure and health services in countries experiencing or recovering from a natural disaster or conflict interrupt routine immunization. Overcrowding in residential camps increases the risk of infection. The COVID-19 pandemic impacted the delivery of routine immunization services and surveillance activities. These setbacks have left many children susceptible to vaccine-preventable diseases such as diphtheria (WHO, 2024a).
Impacts
Diphtheria remains a significant health problem in countries with poor routine vaccination coverage or pockets of unimmunised (WHO, 2017).
The symptoms of diphtheria usually begin 2–5 days after exposure to the bacteria. Typical symptoms of the infection include a sore throat, fever, swollen neck glands and weakness. Within 2–3 days from infection, the dead tissue in the respiratory tract forms a thick, grey coating that can cover tissues in the nose, tonsils and throat, making it hard to breathe and swallow (WHO, 2024a).
Most severe diseases and deaths from diphtheria occur as a result of the diphtheria toxin and its effects. Complications can include inflammation of the heart and nerves (WHO, 2024a).
For unvaccinated individuals without adequate treatment, diphtheria can be fatal in around 30% of cases, with children younger than 5 years of age at greater risk of dying. Any non-immune person (not vaccinated or under-vaccinated) can become infected (WHO, 2024a).
The risk of complications or death decreases considerably if appropriate treatment is provided early in the course of illness. For this reason, if diphtheria is suspected, testing to confirm the disease should be done promptly and treatment should be started as soon as possible. Cases of diphtheria are usually treated with diphtheria antitoxin as well as antibiotics. Diphtheria-specific antitoxin neutralizes circulation toxin in the blood (WHO, 2024a).
Multi-hazard context
Before the introduction of diphtheria vaccine and widespread vaccination in the 1930s, cases occurred throughout the world (WHO, 2024a).
Recently, as a result of undervaccination, outbreaks have been occurring with increasing frequency despite the availability of a safe and effective vaccine (WHO, 2024a).
Damaged health infrastructure and health services in countries experiencing or recovering from a natural hazard or conflict interrupt routine immunization. Overcrowding in residential camps increases the risk of infection (WHO, 2024a).
Risk Management
Diphtheria can be prevented by vaccines that are often given in combination with tetanus and pertussis, and other diseases (WHO, 2024a).
WHO recommends a total of 6 diphtheria-containing vaccine doses be given starting at 6 weeks of age through adolescence to provide long-term protection. Community-wide vaccination with high coverage as a part of routine immunization services embedded in primary health care is the most effective way to prevent diphtheria. All children should be vaccinated against diphtheria with a full primary series and 3 additional booster doses for long-term protection. The vaccine is safe and effective. The diphtheria vaccine is most often combined with vaccines for diseases such as tetanus, pertussis, Hemophilus influenzae, hepatitis B and inactivated polio (WHO, 2024a).
The essential programme on immunization began in 1974. Combination diphtheria vaccines were introduced as part of this programme since its inception and havehttps://www.who.int/publications/i/item/who-wer9231 prevented >90% cases of disease between 1980–2000. In recent years, there have been outbreaks of diphtheria due to inadequate vaccine coverage. To control these outbreaks, WHO has worked with member states in outbreak response and in strengthening routine immunization programmes to improve and sustain immunization coverage to prevent diphtheria infections and deaths (WHO, 2024a).
Monitoring
WHO supports countries to conduct all-hazards strategic risk assessment in the contexts of health emergencies and disasters, which results in the development of a country risk profile. Empowered with the country risk profile, inclusive of a seasonal risk calendar, countries can anticipate potential emergencies before they occur to trigger early alerts and inform early actions (WHO, 2021).
WHO's Early Warning, Alert and Response System (EWARS) has been designed to improve disease outbreak detection in emergency settings, such as in countries in conflict or following a disaster from natural hazards. It is a simple and cost-effective way to rapidly set up a disease surveillance system. EWARS is deployed during an emergency as an adjunct to the national disease surveillance system. WHO works with Ministries of Health and health sector partners to train local health workers to use the system. After the emergency, EWARS should re-integrate back into the national system (WHO, 2023).
References
WHO, 2016. International Health Regulations (2005), 3rd ed. World Health Organization (WHO). Accessed 25 May 2025.
WHO, 2017. Diphtheria vaccines: WHO position paper – August 2017 Weekly Epidemiological Record, 2017, vol. 92, 31. World Health Organization (WHO). Accessed 25 May 2025.
WHO, 2021. Strategic toolkit for assessing risks (STAR): a comprehensive toolkit for all-hazards health emergency risk assessment. World Health Organization (WHO). Accessed 26 May 2025.
WHO, 2023. Early Warning, Alert and Response System (EWARS). World Health Organization (WHO). Accessed 26 May 2025.
WHO, 2024a. Diphtheria. World Health Organization (WHO). Accessed 25 May 2025.
WHO, 2024b. Laboratory testing for diphtheria in outbreak settings: Interim guidance. World Health Organization (WHO). Accessed 16 February 2025.
WHO, 2024c. Clinical management of diphtheria: guideline. World Health Organization (WHO). Accessed 16 February 2025.
WHO, 2025. Diphtheria reported cases and incidence. World Health Organization (WHO). Accessed 16 February 2025.