Whooping Cough Returns With Deadly Force in Northern Nigeria, Five-Year Data Show

Pertussis, better known as whooping cough, is quietly re-emerging in one of Nigeria’s most populous northern states, and the numbers emerging from a new five-year surveillance analysis are sobering. A retrospective study of 768 laboratory-supported, case-based reports from Jigawa State has documented a steady climb in attack rates between 2019 and 2023, culminating in a 2023 outbreak that accounted for every pertussis-related death recorded during the entire study period. The findings, published in BMC Infectious Diseases, offer one of the most detailed pictures yet of how a vaccine-preventable disease that many global health planners assumed was in retreat is finding fresh traction in a region with persistent immunization gaps.

The research team, led by Usman Muhammad Ibrahim of the Department of Community Medicine at Federal University Dutse and Rasheed Shekoni Federal University Teaching Hospital, together with collaborators from the World Health Organization and several Nigerian teaching hospitals, mined the state’s Integrated Disease Surveillance and Response system, the standardized reporting framework through which health facilities across Nigeria log suspected cases of epidemic-prone diseases. Their analysis covered cases reported between 2019 and 2023, with the patient’s survival status, alive or died, serving as the primary outcome. Data were analyzed in SPSS version 22, with statistical significance set at the conventional 5 percent threshold, and the team applied both unadjusted comparisons and an adjusted regression model to disentangle the factors driving mortality.

The demographic profile of the cases tells its own story. Patients ranged in age from 8 to 180 months, with a median of 60 months, meaning the typical patient was a five-year-old, and an interquartile range of 36 to 84 months. That skew toward school-age children is notable, because pertussis vaccination schedules in most of Africa target infants and toddlers, leaving older children vulnerable as vaccine-induced immunity wanes. The seasonal pattern was equally striking: cases clustered early in the year, with 51.6 percent of all reports falling within epidemiological weeks 1 through 13, and the median reporting week sitting at week 13 of a possible range that stretched from week 2 to week 39.

Geographically, the burden was far from uniform. Cases were reported from only 14 of Jigawa State’s 27 local government areas, and a single district, Auyo, accounted for the largest share at 18.7 percent of all cases. This clustering matters for outbreak response, because it suggests that transmission was concentrated in specific communities rather than diffused evenly across the state, and it gives program managers a concrete starting point for targeted vaccination campaigns and active case-finding.

The mortality figures are where the study becomes genuinely alarming. The overall case-fatality rate across the five years was 7.3 percent, an extraordinarily high figure for a disease that kills fewer than one in a hundred symptomatic patients in well-resourced settings. Death was most frequent among children aged 5 to 9 years, who died at a rate of 8.5 percent, followed by children under five at 7.1 percent. Even more telling, every single pertussis-related death in the dataset, representing 16.9 percent of the cases recorded that year, occurred during the 2023 outbreak. In other words, the disease did not merely become more common as the study period progressed; it became dramatically more lethal.

The year-by-year attack rates trace the re-emergence in fine detail. In 2019, rates stood at 5.0 per 100,000 among both children under five and children aged 5 to 9 years, compared with just 0.6 per 100,000 among adolescents. The pandemic year of 2020 brought a decline to 2.0 per 100,000 in both child groups, a dip consistent with the movement restrictions and reduced transmission of many respiratory pathogens during that period. In 2021, children aged 5 to 9 years carried the highest burden at 2.1 per 100,000. Then the curve bent sharply upward: 2022 saw rates jump to 7.4 per 100,000 among under-fives and 6.3 per 100,000 among 5-to-9-year-olds, while adolescents recorded 0.3 per 100,000. By 2023, the rates had climbed again to 10.2 per 100,000 among under-fives, 8.8 among 5-to-9-year-olds, and 5.1 among adolescents, the first year in which adolescent transmission rose substantially.

The statistical modeling revealed a set of mortality predictors that will unsettle many readers. Mortality was significantly higher in the Northeast Senatorial Zone of the state, where 14.4 percent of cases died, compared with the rest of Jigawa, and dramatically higher during the 2023 outbreak, when the case-fatality rate reached 16.9 percent. Both associations were highly significant, with p values below 0.001. But the most counterintuitive finding concerned vaccination status: children documented as vaccinated had a mortality rate of 15.4 percent, and in the adjusted analysis, unvaccinated cases actually had 80 percent lower odds of dying than vaccinated cases, with an adjusted odds ratio of 0.20 and a 95 percent confidence interval of 0.10 to 0.30.

The authors are careful to frame this vaccination paradox in terms of what it likely reflects rather than what it might naively suggest. Vaccination status recorded in surveillance data is a marker of a complex web of factors, including the severity of illness that brings a child to a health facility, the completeness of the records, and the possibility that children with documented vaccination are those who had enough prior contact with the health system to be counted. The finding underscores, rather than undermines, the study’s central recommendation: routine immunization coverage must be strengthened, and seroprevalence studies are needed to map immunity gaps, particularly among older age groups who appear to be sustaining transmission. Waning immunity in vaccinated children, a well-documented feature of pertussis epidemiology worldwide, remains a plausible contributor that only serological surveys can properly quantify.

Two other independent predictors of death emerged from the adjusted model, and both point to the same underlying problem of late and inadequate clinical care. Outbreak timing mattered enormously: compared with outbreaks occurring at epidemiological week 26 or later, cases arising during weeks 1 through 13 had 95 percent lower odds of mortality, with an adjusted odds ratio of 0.05 and a confidence interval of 0.02 to 0.10, and those during weeks 14 through 25 had 90 percent lower odds, at an adjusted odds ratio of 0.10. The authors interpret this as evidence that cases presenting late in outbreak periods, when health systems are overwhelmed and community awareness has faded, fare far worse. Hospital admission itself carried an approximately tenfold higher odds of death, with an adjusted odds ratio of 10.2 and a confidence interval of 5.7 to 18.2, a signal that admitted patients were those arriving with severe, advanced disease, and that delays in presentation were funneling the sickest children into hospitals too late for effective intervention.

Taken together, the Jigawa data sketch a disease that is exploiting every weakness in the local health architecture: gaps in routine immunization, waning protection in older children, delayed care-seeking, and surveillance that captures only part of the true burden. The study’s authors call for strengthened case-based surveillance, earlier detection of outbreaks, improved clinical management of hospitalized cases, and renewed investment in routine immunization, complemented by seroprevalence research to identify the immunity gaps driving transmission. For a disease preventable by one of the oldest and cheapest vaccines in the global arsenal, the message from northwest Nigeria is difficult to ignore. Pertussis has not disappeared from the world’s public health agenda; in places where the systems meant to contain it have frayed, it is reasserting itself with lethal efficiency, and the five-year record from Jigawa State is now among the clearest warnings available.

Subject of Research: Epidemiological trends and mortality of pertussis (whooping cough) in Jigawa State, northwest Nigeria, based on five years of case-based surveillance data

Article Title: Epidemiological trends and pertussis-related mortality in Jigawa State, Northwest Nigeria: evidence from five years of case-based surveillance

Article References: Ibrahim, U. M., Kofi, B., Babura, S. M., Bassey, B. E., Also, U., Danzomo, A. A., El-Yakub, F. A., Yusuf, S., Borodo, A. M., Yusuf, S., Dania, O. M., Nashabaru, I., & Jibo, A. M. (2026). Epidemiological trends and pertussis-related mortality in Jigawa State, Northwest Nigeria: evidence from five years of case-based surveillance. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14511-z

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14511-z

Keywords: pertussis, whooping cough, Nigeria, Jigawa State, epidemiology, surveillance, outbreak, case-fatality rate, immunization, vaccine-preventable disease, public health, re-emerging infectious disease