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Descriptive Epidemiology of Coronavirus Disease 2019 in Nigeria, 27 February-6 June, 2020

Our take —

This retrospective analysis of national COVID-19 surveillance data provides insights about the epidemiology of the pandemic in Nigeria. The 12,289 confirmed COVID-19 cases translated to a national cumulative incidence of 5.6 cases per 100,000 population, and 342 (2.8%) died. Confirmation of each COVID-19 case through real-time polymerase chain reaction was a strength of the study. However, the substantial proportions of suspected and probable cases for whom a definitive diagnoses was not obtained, as well as missing key socio-demographic and clinical variables present major limitations for the study, and likely lead to bias in estimates of socio-demographic factors and clinical outcomes reported, including a potential overestimation of the case fatality.

Study design

Retrospective Cohort

Study population and setting

This study describes the epidemiology of COVID-19 in Nigeria from February 27, 2020, when the first case was confirmed in the country, up to June 6, 2020. Beginning in 2017, The Nigeria Centers for Disease Control and Prevention (NCDC) used an open-source real-time electronic health surveillance database (called SORMAS) as the primary digital surveillance platform for implementing its Integrated Disease Surveillance and Response (IDSR) system. In January 2020, a COVID module was developed and added. The current study was a retrospective analysis of national surveillance data captured in SORMAS for individuals assessed for SARS-CoV-2. According to guidelines in place during the period, samples were to be collected from suspected COVID-19 cases (i.e., symptoms with history of international travel; symptoms and contact with confirmed or probable cases; or acute respiratory illness in an area with moderate to high prevalence of COVID-19 with no other explanation). Health care workers completed case investigation forms and collected one nasopharyngeal or nasal swab, and one oropharyngeal swab. Samples were analyzed at designated NCDC-certified laboratories in the country.

Summary of Main Findings

Among 60,839 COVID-19 related records in the SORMAS database, a total of 40,926 showed evidence of SARS-CoV-2 by RT-PCR (i.e., 12,289 confirmed cases and 28,637 non-cases). Cumulative incidence of COVID-19 in the country was estimated at 5.6 per 100,000 population. Of the 12,289 confirmed cases, complete record of clinical outcome was available for 3467 (28.2%), and 342 (2.8%) died. Mean age of confirmed cases was 37.1 years (SD: 15.7), and 65.8% were men. Among confirmed cases with occupation information, 9.3% were health care workers. The proportion of cases reporting travel locally (4.3%) or internationally (1.6%) in the 14 days before diagnosis was low. Among 111 cases for whom information was available on hospitalization, median length of hospital stay was 19 days. About 66% of cases had not shown symptoms in the 14 days before diagnosis. Fever and cough were the most common symptoms. Estimated cumulative incidence was highest in Lagos state (39.9 per 100,000 population), and in the capital, Abuja (19.4 per 100,000 population).

Study Strengths

Confirmation of each COVID-19 case was established through real-time polymerase chain reaction (RT-PCR) at NCDC-certified labs.


There was a high proportion of missing data on major indicators and socio-demographic factors; the authors reported that major efforts were underway to improve completeness and quality of data entered into the database to >90%. Guidelines for whom should be tested for SARS-CoV-2 were not uniformly followed.

Value added

This study provides a national description of COVID-19 epidemiology during the first wave of the pandemic in Nigeria.

This review was posted on: 23 October 2020