Ikejezie, Juniorcaius
(2025)
Disentangling diphtheria: an investigation into its persistence worldwide.
PhD thesis, University of Nottingham.
Abstract
Introduction: Diphtheria is a contagious disease primarily caused by Corynebacterium diphtheriae, which typically affects the respiratory tract and less often the skin. Transmission occurs via exposure to secretions of an infected person. Generally, respiratory diphtheria has a case fatality rate of 5–10%, with higher rates seen among certain groups (e.g., untreated, unvaccinated individuals). After years of decline, diphtheria is experiencing a resurgence, with 24,778 cases reported in 2023 – the highest global case count in over 20 years. The disease has severely affected Haiti, a country that is also facing vulnerability to natural disasters, concurrent health crises, and civil unrest. Despite its impact, diphtheria is still relatively understudied, with questions remaining about the determinants of the observed epidemiological trends and patterns. This PhD thesis aimed to explore drivers of global diphtheria persistence to fill current knowledge gaps.
Methods: The thesis consisted of three studies. The first study was a systematic review and meta-analysis to identify risk factors for diphtheria. The second study was a spatial analysis of the epidemiology of the disease in Haiti between December 2014 and June 2021 to examine the spatiotemporal distribution of cases, detect diphtheria hotspots, and identify potential risk factors for the disease. The third study was a mixed-methods analysis of posts shared from January 2012 to December 2022 on X (formerly Twitter) to understand global perceptions and attitudes towards diphtheria.
Results: The review identified three potential risk factors for diphtheria: incomplete vaccination, contact with a person with skin lesions, and low diphtheria knowledge. Evidence for other risk factors was less conclusive. The spatial analysis revealed that the reported diphtheria case rate exhibited spatial variability in Haiti, with nine out of 140 communes being classified as hotspots. This rate was positively associated with the number of healthcare facilities per 100,000 inhabitants and the proportion of urban population, while it had a negative association with female literacy. The mixed-methods analysis showed that a diversity of voices participates in diphtheria-related conversations on X, leading to the identification of various themes – with vaccination being the predominant topic of interest. The analysis also highlighted posts spreading false information alongside differences in tone and content between high-burden and low-burden countries, mirroring variations in healthcare priorities and challenges.
Conclusion: This thesis illustrates the complex nature of diphtheria, as evidenced by the multitude of biological, immunological, environmental, socioeconomic, behavioural, and informational factors that potentially contribute to the persistence of the disease. The in-depth investigation of diphtheria in Haiti highlighted the compounded difficulties in controlling the disease during a humanitarian crisis. Findings from this case study, alongside the risk factors and themes identified through the systematic review and mixed-methods analysis, can inform future research and interventions not only in Haiti but also in other countries facing similar challenges. While remaining context-specific, these interventions should seek to raise vaccination coverage, scale up access to healthcare services, strengthen surveillance systems, increase health literacy, and improve sanitation and hygiene conditions. Innovative tools like spatial analysis and social media monitoring can enhance surveillance, by facilitating the detection of disease trends, at-risk populations, and emerging public concerns.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Lewis, Sarah
Langley, Tessa
Phalkey, Revati
Bisanzio, Donal |
| Keywords: |
Diphtheria, Risk factors, Spatial analysis, Epidemiology, Public Health, Vaccination, Infectious diseases |
| Subjects: |
W Medicine and related subjects (NLM Classification) > WC Communicable diseases |
| Faculties/Schools: |
UK Campuses > Faculty of Medicine and Health Sciences > School of Medicine |
| Item ID: |
80258 |
| Depositing User: |
Ikejezie, Juniorcaius
|
| Date Deposited: |
23 Jul 2025 04:40 |
| Last Modified: |
23 Jul 2025 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/80258 |
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