Diphtheria resurgence, drug-supply delays, and case fatality at a tertiary hospital in Adamawa State, north-eastern Nigeria: a retrospective cohort study (2023–2026)

Background

Diphtheria caused by toxigenic Corynebacterium diphtheriae re-emerged in Nigeria from December 2022 as the country’s largest ever recorded outbreak, accumulating over 20,000 suspected cases and 872 confirmed deaths by December 2025. The Borno-Adamawa-Yobe (BAY) states zone in north-eastern Nigeria is a recognised high-vulnerability cluster, yet no facility-level, longitudinal epidemiological data from Adamawa State have been published.

Methodology/Principal findings

We conducted a retrospective cohort study of all patients admitted with diphtheria to the Isolation Ward of Modibbo Adama University Teaching Hospital (MAUTH), Yola — the sole federal university teaching hospital in Adamawa State — from January 2023 to April 2026, using prospective admission register records. Sixty-one patients were identified (17.9% of 330 total isolation admissions). Admissions escalated 580% from 5 (2023) to 34 (2025). Median age was 8.0 years; 91.8% were under 15 years. The overall in-hospital case fatality rate (CFR) was 41.5% (22/53 known outcomes; 95% confidence interval: 29.0–55.0%). Annual CFR declined from 60.0% (2023) to 28.6% (2025), temporally consistent with improving diphtheria antitoxin access. A critical operational finding was the persistent shortage of intravenous erythromycin — the mandated antibiotic for patients unable to swallow — compelling oral administration in patients with pharyngeal pseudomembrane and dysphagia. Respiratory distress at presentation carried an 80% CFR; cardiac complication, 100%. Age and sex were not statistically significant mortality predictors. Gombi local government area contributed 16.4% of cases — the highest burden among non-capital communities — consistent with its role as a population movement corridor from Borno State’s outbreak epicentre. A September–October seasonal peak (47.5% of admissions) was identified, diverging from the national January–April pattern.

Conclusions/Significance

This study provides the first peer-reviewed, facility-level diphtheria epidemiological dataset from Adamawa State. The in-hospital CFR substantially exceeds national surveillance averages due to referral bias and historical drug supply constraints. The declining CFR against rising admissions signals improving case management. Pre-positioning of diphtheria antitoxin and intravenous erythromycin before each August–October peak, accelerated childhood immunisation catch-up, and strengthened surveillance in Adamawa State are identified as urgent priorities.

Author summary

Diphtheria is a throat infection caused by bacteria that produce a toxin capable of damaging the heart and nerves. It is preventable by childhood vaccination, but large outbreaks occur when vaccination rates fall. Nigeria is currently experiencing its worst recorded diphtheria outbreak, with over 20,000 cases and nearly 900 deaths since late 2022.

We studied all diphtheria patients admitted to Modibbo Adama University Teaching Hospital in Yola, north-eastern Nigeria — the region’s only federal teaching hospital — over three and a half years. We found that admissions more than tripled in that period, nearly 9 in 10 patients were children under 15, and over 4 in 10 who had a documented outcome died in hospital. One of our most important findings was a shortage of intravenous antibiotic medicine: patients with severe throat infection cannot swallow tablets, but the injectable form was repeatedly unavailable, forcing the team to crush tablets or use stomach tubes in critically ill children — a dangerous workaround.

We identified a distinctive peak in September and October, and a rural cluster in Gombi that appears to receive patients from the neighbouring state with the highest national burden. Our study highlights that reliable supply of the correct antibiotic formulation, continued vaccination campaigns, and advance planning for the seasonal peak could save children’s lives in this under-resourced region.