WHO Diphtheria Laboratory Diagnosis
Diphtheria remains a serious and potentially life-threatening vaccine preventable disease. Accurate laboratory diagnosis is essential for detecting cases, guiding treatment, monitoring transmission, and supporting public health action.
1. Why Diphtheria Surveillance Matters
Despite the availability of highly effective vaccines, diphtheria continues to occur in areas where vaccination coverage is inadequate, or immunity gaps exist.
Laboratory confirmation plays a critical role in:
- Identifying outbreaks in a timely manner
- Confirming transmission chains
- Supporting patient management
- Monitoring disease burden
- Informing immunization strategies
- Strengthening national surveillance systems
Because diphtheria has become uncommon in many countries, laboratory expertise and routine recognition of the disease have declined. Maintaining diagnostic readiness is therefore essential.
2. What Causes Diphtheria?
Diphtheria is caused by toxin-producing bacteria belonging to the Corynebacterium genus, including:
| Species
| Public Health Importance |
| Corynebacterium diphtheriae | Primary cause of human diphtheria |
| Corynebacterium ulcerans | Emerging zoonotic cause of diphtheria-like disease |
| Corynebacterium pseudotuberculosis | Rare cause of diphtheria toxin-mediated infection |
The production of diphtheria toxin is responsible for severe clinical manifestations and potentially fatal complications.
3. WHO Laboratory Manual
The latest WHO laboratory manual for the diagnosis of diphtheria and other related infections provides comprehensive guidance on:
- Diphtheria case definitions and surveillance standards
- Specimen collection and transport
- Culture and bacterial identification methods
- Toxigenicity testing
- Molecular diagnostics (PCR and sequencing)
- Serological methods
- Antimicrobial susceptibility testing
- Laboratory quality management
- Biosafety and biosecurity
- Diphtheria outbreak investigation support
The manual has been expanded to address all potentially toxigenic Corynebacterium species and reflects major advances in laboratory science and public health surveillance.
4. WHO Diphtheria Collaborating Centres
WHO further strengthened its commitment to fighting diphtheria by designating the Bavarian Health and Food Safety Authority in Germany and the UK Health Security Agency (UKHSA) as its collaborating centres.
The WHO Diphtheria Collaborating Centres support countries in strengthening diagnostic capacity, standardizing laboratory practices, enhancing surveillance systems, and ensuring rapid identification of diphtheria and other toxigenic corynebacterial infections.
A. Key focus areas:
- Early laboratory confirmation of suspected cases
- Detection of toxigenic Corynebacterium species
- Quality assured laboratory diagnostics
- Integration of molecular technologies into surveillance
- Global laboratory collaboration and capacity building
B. The WHO Diphtheria Collaborating Centers work to:
- Standardize Diagnostics: Promote harmonized laboratory methods and quality-assured testing worldwide.
- Build Capacity: Strengthen national and regional laboratory expertise through training and technical support.
- Improve Surveillance: Support integration of laboratory data into national, regional and global surveillance systems.
- Foster Collaboration: Facilitate information sharing among reference laboratories and public health institutions.
- Advance Innovation: Encourage adoption of molecular tools and emerging technologies for improved disease detection.
5. Diphtheria Outbreak Resources
WHO has developed a diphtheria outbreak investigation tool that can be used to tract outbreaks. The tool provided information on:
- Case definitions
- Reporting protocols
- Outbreak investigation tools
- Data management guidance
