Diphtheria has killed 1,252 people across eight African countries this year
WHO has graded the regional resurgence a level 2 emergency. Only 5.7% of the 20,412 suspected cases were laboratory-confirmed, and the antitoxin that prevents most deaths is in global short supply.
From 1 January to 2 November this year, eight countries in the WHO African Region reported 20,412 suspected cases of diphtheria and 1,252 deaths — an average case fatality ratio of about 6% [s1]. WHO set out the regional picture in a Disease Outbreak News notice published on 21 November, and has graded the resurgence a grade 2 emergency under its Emergency Response Framework [s1].
The eight countries are Algeria, Chad, Guinea, Mali, Mauritania, Niger, Nigeria and South Africa [s1]. Several have had continuous outbreaks since 2023 [s1].
A disease that should not still be doing this
Diphtheria is vaccine-preventable and treatable. Its damage comes from a toxin produced by toxigenic Corynebacterium diphtheriae, which causes myocarditis, kidney failure and neurological injury [s1]. Treatment rests on two things: antibiotics — azithromycin or penicillin — and diphtheria antitoxin, which neutralises circulating toxin [s1]. With antitoxin available, diphtheria is fatal in roughly 5 to 10% of cases; where access to it is poor, the case fatality ratio can reach 40% [s1].
The age distribution in this outbreak is the tell. Women, children aged 5 to 18, and young adults under 30 are the most affected, which WHO reads as confirmation that the immunity gap extends well beyond early childhood [s1]. That is a signature of years of missed routine doses rather than a single failed campaign.
Nigeria carries most of it
Nigeria accounts for the largest share by a wide margin: 12,150 suspected cases, 8,587 confirmed, and 884 deaths, a case fatality ratio of 7.2%, with confirmed cases in 240 Local Government Areas across 30 states [s1]. Only 3% of Nigerian cases were confirmed by laboratory testing; most are clinically compatible diagnoses [s1]. More than two million Nigerian children are under-immunized, including zero-dose children [s1]. WHO/UNICEF estimates for 2024 put Nigeria's coverage at 71% for the first DTP dose and 67% for the third [s1].
Guinea has the highest case fatality ratio of the affected countries: 476 suspected cases and 123 deaths since June, a ratio of 25.8% among suspected cases, with over 80% of cases and fatalities in Siguiri district in the Kankan region — gold-mining areas with high population mobility [s1]. Only 70 cases have been laboratory-confirmed [s1]. Guinea's 2024 immunization coverage was 77% for the first DTP dose and 63% for the third [s1].
Chad reported 4,462 suspected cases and 47 deaths with only four laboratory-confirmed cases, across 27 of 215 health districts [s1]. Niger reported 1,926 suspected cases and 122 deaths (6.3%), with 765 laboratory-confirmed, across 34 of 72 health districts [s1] — fewer cases and deaths than in 2024, but with transmission still active [s1].
Mali's outbreak is expanding fastest: 430 suspected cases and 29 deaths (6.7%), across seven of 11 regions including Bamako, with affected districts rising from three to 30 out of 75 in under six weeks [s1]. Mauritania declared its outbreak on 25 September after an initial delay and has since recorded 849 suspected cases and 33 deaths (4%) across 11 of 53 departments, with only 10% of cases having a documented vaccination history — and it is running that response alongside a Rift Valley fever outbreak in some of the same regions [s1].
Two smaller outbreaks round out the list. Algeria reported 13 suspected cases and two deaths in Skikda province in October, eight laboratory-confirmed, none of them vaccinated [s1]. South Africa reported 106 cases from 1 January to 26 October — 66 laboratory-confirmed respiratory cases, two cutaneous, one probable respiratory case and 37 asymptomatic carriers — across five of nine provinces, with a case fatality ratio of 18% among probable and confirmed respiratory cases and most cases in adults aged 18 and over [s1].
The two bottlenecks
The first is diagnosis. Of the 20,412 suspected cases, 9,864 (48.3%) have been confirmed through laboratory testing, epidemiological linkage or clinical diagnosis — but laboratory confirmation specifically was performed for only 5.7% of suspected cases, 1,177 in total [s1]. Shortages of diagnostic supplies, weak specimen transport and limited technical capacity mean the true size of the outbreak is unclear in both directions [s1].
The second is treatment. Equine diphtheria antitoxin has been the cornerstone of treatment for toxin-mediated disease since 1890 [s2]. A review published in January in Memórias do Instituto Oswaldo Cruz — written before this year's surge — traced how a therapy invented more than 130 years ago is still in use, still effective, and still made by hyperimmunising horses, with a scarce international supply under persistent threat and alternative therapeutic strategies not yet arrived [s2]. WHO's notice names that global shortage, alongside uneven clinical capacity to administer the product, as a significant constraint on effective case management [s1].
What is being done
Response operations vary by country but share a core: active case finding and timely reporting, clinical management with antitoxin and antibiotics per WHO guidelines, infection prevention and control, risk communication, and training [s1]. Reactive vaccination campaigns have run in Imo, Kaduna and Lagos in Nigeria, and in Mauritania; Niger ran a campaign in September [s1]. Chad and Nigeria have both approached Gavi for vaccine supply and operational funding [s1].
WHO assesses the regional public health risk as high, citing the potential for further geographic expansion, high fatality rates, insufficient resources and weak surveillance and laboratory systems [s1]. The global risk is assessed as low, since most countries outside the region have established immunization programmes and adequate surveillance, though importation through travel cannot be ruled out [s1]. WHO rates its confidence in the available information as moderate [s1].
For context on scale: between 2000 and 2024 the African Region reported 75,789 suspected diphtheria cases, the majority of them in 2023 and 2024 alone, when roughly 57,000 suspected cases and 2,000 deaths were recorded across nine countries [s1]. This is not a new emergency. It is the third consecutive year of one.
Sources
- [s1] Diphtheria - African Region (AFRO), World Health Organization, 21 November 2025. https://www.who.int/emergencies/disease-outbreak-news/item/DON588
- [s2] Diphtheria antitoxin treatment: from pioneer to neglected, Memórias do Instituto Oswaldo Cruz, 20 January 2025. https://doi.org/10.1590/0074-02760240214
Sources
- Diphtheria - African Region (AFRO) — World Health Organization , November 21, 2025
- Diphtheria antitoxin treatment: from pioneer to neglected — Memórias do Instituto Oswaldo Cruz , January 20, 2025
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