Two Years of Testing Reveal Who Carried COVID-19 in Southeastern Nigeria

When the World Health Organization declared COVID-19 a pandemic on March 12, 2020, few health systems in the world were braced for what followed. Nigeria recorded its first case on February 28, 2020, and within weeks the virus had spread from the commercial hub of Lagos to all 36 states and the Federal Capital Territory. For a country with a large rural population, uneven laboratory infrastructure, and a surveillance network still being built out, the challenge was not only treating the sick but understanding who, exactly, was becoming infected. A new study from Ebonyi State in Southeastern Nigeria now offers one of the most detailed demographic pictures of the pandemic in that region, drawn from two full years of systematic testing.

The research, conducted by a team led from the Virology Laboratory of Alex Ekwueme Federal University Teaching Hospital in Abakaliki, set out to perform a comprehensive surveillance of COVID-19 incidence across Ebonyi State. Between April 2020 and March 2022, a span of 24 calendar months, the team collected clinical swab samples from 42,918 individuals suspected of having COVID-19 symptoms. The sample set was dominated by nasopharyngeal swabs, which accounted for 42,611 of the specimens, supplemented by 200 oropharyngeal swabs and 107 nasal swabs. Every sample was processed and analyzed by quantitative reverse transcription polymerase chain reaction, or qRT-PCR, the molecular technique that remains the reference standard for confirming SARS-CoV-2 infection because it directly detects viral RNA rather than the antibodies or antigens measured by faster but less specific tests.

The headline finding is stark: of the 42,918 people examined, 13,683 were confirmed positive by PCR, a positivity rate of 31.9 percent. That figure is notable in itself. In many surveillance settings, positivity rates among symptomatic suspects fluctuate widely with the intensity of transmission, but a sustained rate above 30 percent across two years of testing suggests that by the time individuals reached testing, a substantial fraction were genuinely infected. It also reflects the reality of a testing strategy that prioritized symptomatic suspects rather than broad community screening, a pragmatic choice in a resource-limited setting but one that means the study captures the face of clinically suspected disease rather than silent community transmission.

Sex emerged as one of the clearest dividing lines in the data. Infections were more predominant among males, at 33.7 percent of the 23,562 men tested, than among females, at 29.6 percent of the 19,356 women. This pattern echoes findings from many parts of the world, where biological differences in immune response, including sex hormone effects on antiviral pathways, have been proposed as one contributor, alongside behavioral factors such as occupational exposure and mobility. In the Southeastern Nigerian context, the higher male positivity may also reflect the structure of daily economic life, since men in the region’s markets and transport networks often work in crowded, high-contact environments that favor respiratory transmission.

Age told an equally revealing story. The age group with the highest number of infected individuals was 31 to 40 years, followed by those aged 41 and above. This is the demographic backbone of the workforce, the people who staff markets, drive vehicles, farm, teach, and run households. Their prominence among confirmed cases underscores a central tension of the pandemic in Africa: while severe disease and death concentrated among the elderly globally, the engine of transmission in many African settings was the young and middle-aged working population, who could not simply stay home. Perhaps most striking, children accounted for only 0.1 percent of confirmed cases. Whether this reflects genuinely lower infection rates among children, fewer symptomatic presentations that would trigger testing, or lower rates of testing in pediatric populations, the near-absence of children in the surveillance record is itself an important data point for future outbreak planning.

Education level, an indicator rarely captured in routine viral surveillance, proved to be strongly associated with infection. The highest frequency of cases, 35 percent, was observed among individuals with no formal education, followed by those with primary education at 27.8 percent. The lowest incidence, 15.4 percent, was recorded among individuals with secondary education. The gradient is unlikely to be a simple causal story. Educational attainment in Nigeria correlates closely with occupation, income, housing density, access to health information, and the ability to adopt protective behaviors such as masking, distancing, and early presentation for testing. People without formal education are more likely to work in informal, contact-intensive trades and less likely to encounter public health messaging delivered through formal channels. The data therefore map infection onto the social geography of disadvantage, showing that in Ebonyi State the burden of suspected and confirmed COVID-19 fell disproportionately on those least equipped to navigate the pandemic’s information environment.

Occupation sharpened that picture further. Traders recorded the highest incidence of any occupational category, at 41.4 percent, followed at a considerable distance by students at 9.7 percent. The dominance of traders is consistent with the structure of Southeastern Nigeria’s economy, where open-air and enclosed markets are dense nodes of daily interaction, drawing thousands of buyers and sellers into prolonged proximity. Market settings combine the risk factors that respiratory viruses exploit best: crowding, shared surfaces, prolonged indoor contact, and limited capacity for ventilation or physical distancing. For pandemic planners, the message is unambiguous. In this region, markets are not merely places of commerce but critical nodes of transmission, and any future response that does not integrate market-based testing, ventilation improvements, and targeted risk communication will leave the largest reservoir of infection untouched.

The study’s methodological backbone deserves attention as a model for regional surveillance. Samples were transported in viral transport medium, a buffered solution that preserves viral RNA and infectious particles between collection and testing. Detection relied on qRT-PCR targeting the viral genome, with the RNA-dependent RNA polymerase gene among the canonical targets used to confirm SARS-CoV-2. Cycle-threshold values, which inversely reflect viral load, provide the quantitative readout that distinguishes true infection from contamination. The surveillance was embedded in the Virology Department of Alex Ekwueme Federal University Teaching Hospital, with case investigation forms feeding into systems aligned with the Surveillance Outbreak Response Management and Analysis System used by the Nigeria Centre for Disease Control and Prevention. Ethics approval came from the Ebonyi State Ministry of Health, and informed consent was obtained from all participants in line with the Declaration of Helsinki. The study received no external funding, a detail that speaks to the institutional commitment required to sustain two years of molecular testing in a state laboratory.

What does this snapshot mean for the future? The authors frame their findings as a guide to preparedness and response, and the demographic signature they document points to concrete priorities. Any respiratory outbreak response in Southeastern Nigeria should, on this evidence, concentrate testing and vaccination outreach on working-age adults, particularly men in the trading sector; design health communication for populations without formal education, using local languages, radio, and community intermediaries rather than text-based formal channels; and treat markets as priority sites for surveillance and mitigation. The near-invisibility of children in the case record should prompt targeted pediatric serosurveys to determine whether children were truly spared or simply untested, since that distinction changes the mathematics of herd immunity and school-based transmission.

There are also broader lessons for global health equity. Much of the world’s pandemic data came from high-income countries with dense genomic and case-based surveillance, leaving large gaps across sub-Saharan Africa. Studies like this one, built on sustained local laboratory capacity rather than short-term imported teams, demonstrate that rigorous molecular epidemiology is achievable in state-level facilities and that the resulting data can be directly actionable. The 31.9 percent positivity rate, the male excess, the concentration among traders and the uneducated, and the near-absence of children together form a demographic fingerprint that no imported model could have predicted. As the world prepares for the next respiratory pandemic, the experience of Ebonyi State suggests that the most valuable surveillance assets are not only sequencers and reagents but the patient accumulation of local, demographically detailed evidence, gathered one swab at a time over years rather than weeks.

Subject of Research: Demographic patterns of COVID-19 incidence in surveillance testing in Southeastern Nigeria

Article Title: A snapshot of the demographic dynamics of COVID-19 surveillance in Southeastern Nigeria

Article References: Odeh, E. C., Iroha, C. S., Dowe, E., Moses, I. B., Onwe, O. E., Uzodinma, U., Chika-Igwenyi, N. M., Nwuzo, A. C., Agumah, N. B., Nwafor, I. E., Udeze, C., Achi, E. C., Moses, I. E., & Iroha, I. R. (2026). A snapshot of the demographic dynamics of COVID-19 surveillance in Southeastern Nigeria. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14552-4

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14552-4

Keywords: COVID-19, SARS-CoV-2, surveillance, qRT-PCR, epidemiology, Nigeria, Ebonyi State, demographics, public health, nasopharyngeal swabs, traders, health equity