Published in PLOS One on 2026-06-25, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original study title: Spatial distribution of diphtheria cases during the 2022/2023 outbreak in Kano State, Northern Nigeria
Original authors: Rayyan M Garba, Zainab A Umar, Zainab Abdulkadir, Usman Bashir, Rabiu I Jalo, Yasir N Jibril, Aminu A Yusuf, Kabiru I Gurama, Abdullahi K Suleiman, Zainab U Ibrahim, Sherifah Sheriff, Ibrahim D Muhammad, Chizoba Okolo, Adetayo Aborisade, Abdulgafar L Olawumi, Kabiru Abdulsalam, Nafisatu Bello-Muhammad, Umma A Ibrahim, Oiza O Aliu-Isah, Mustapha A Yusuf, Aisha A Galadanci, Jibrin Gambo, Yusuf A Yusuf, Aishatu L Adamu, Baba M Musa, Muktar H Aliyu
Source: PLOS One • DOI 10.1371/journal.pone.0351150
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
After decades of control, a nationwide diphtheria outbreak occurred in Nigeria in 2022, with approximately 75% of confirmed cases reported in Kano state, Nigeria. We assessed the spatial distribution of diphtheria cases in Kano state to identify disease clusters/hotspots. We used national surveillance data on 10,085 confirmed cases of diphtheria in Kano state from April 2022 to December 2023, accessed via the Nigerian Centre for Disease Control and Prevention website. Data were converted to CVS format and analyzed for spatial distribution of diphtheria cases using QGIS-LTR Version 3.34.11. We found clustering of diphtheria cases in the eight metropolitan Local Government Areas (LGAs) of the state, where health facilities were also clustered. Ungogo LGA had the highest clustering of diphtheria cases but the least clustering of health facilities. This study enhances understanding of the spatial dynamics of diphtheria transmission in Nigeria and provides actionable insights for designing targeted interventions and strategies against hotspots to curb transmission and strengthen preparedness for future epidemics.
Introduction
Diphtheria is a serious acute infectious disease caused by toxin-producing strains of gram-positive bacteria, Corynebacterium diphtheriae, primarily transmitted from person to person through respiratory droplets and contact with infected skin lesions [1]. The pathogenicity and virulence of C. diphtheriae are mediated by the production of diphtheria exotoxin, and infection usually results in respiratory (nasal, pharyngeal, or laryngeal) or cutaneous disease [1–3]. Inflammation associated with the diphtheria toxin can result in marked enlargement of the cervical lymph nodes and swelling of surrounding tissues [2,4] and the development of a mucosal pseudo-membrane that can obstruct the airway and and potentially lead to fatal outcomes [5].
Prior to widespread childhood vaccination, it was estimated that approximately 1 million diphtheria cases occurred worldwide, resulting in around 60,000 deaths annually [6]. Following the establishment of the Expanded Programme on Immunization (EPI) in 1974, which initially targeted diphtheria as one of the six deadliest childhood diseases, reported cases declined by >90% between 1980 and 2000 [7]. However, in recent years, diphtheria outbreaks have become more widespread and frequent [8–11]. Although initially limited to vulnerable groups in displaced populations, some outbreaks have also been associated with sub-optimal vaccination coverage and waning of vaccine-induced immunity [8,12]. Sub-optimal coverage and waning immunity can result in successive accumulation of susceptible unvaccinated populations that trigger outbreaks, particularly following immunisation service disruptions that ensued from COVID-19-related restrictions [13,14].
Vaccination coverage has declined globally since the COVID-19 pandemic, with the DTP3 vaccination rate dropping from 86% in 2019 to 81% in 2021, and even lower (56%) in Nigeria, Africa’s most populous country [15–17]. The current diphtheria outbreak started in 2022 and has persisted, and Kano state is the worst afflicted in the country. Between June 2022 and December 2023, a total of 22,293 suspected and 13,387 confirmed diphtheria cases were reported in Nigeria, and Kano state alone accounted for >75% (10,085) of the confirmed cases [18], hence, the reason for the choice of Kano state.
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider hospital systems desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 Rayyan M Garba, Zainab A Umar, Zainab Abdulkadir, Usman Bashir, Rabiu I Jalo, Yasir N Jibril, Aminu A Yusuf, Kabiru I Gurama, Abdullahi K Suleiman, Zainab U Ibrahim, Sherifah Sheriff, Ibrahim D Muhammad, Chizoba Okolo, Adetayo Aborisade, Abdulgafar L Olawumi, Kabiru Abdulsalam, Nafisatu Bello-Muhammad, Umma A Ibrahim, Oiza O Aliu-Isah, Mustapha A Yusuf, Aisha A Galadanci, Jibrin Gambo, Yusuf A Yusuf, Aishatu L Adamu, Baba M Musa, Muktar H Aliyu. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
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