Risk factors for COVID-19 infection and disease severity in Nigeria: a case-control study

INTRODUCTION: identifying risk factors for SARS-CoV-2 infection and disease severity is critical to developing measures to protect vulnerable groups. We aimed to identify risk factors for SARS-CoV-2 infection and severe disease. METHODS: this was an unmatched case-control study that recruited participants in the country from April to July 2020. Cases tested positive on Reverse-Transcription Polymerase Chain Reaction (RT-PCR), while controls tested negative on RT-PCR. Data were collected by trained research assistants using an interviewer-administered questionnaire. Cases were categorized into severe and non-severe to identify risk factors for severe disease. RESULTS: there were 497 cases and 997 controls recruited. Contact with a symptomatic confirmed case adjusted odds ratio (aOR) 1.91 (95% CI: 1.30-2.80) and attendance of mass gatherings aOR 1.74 (95% CI: 1.10-2.74) were associated with SARS-CoV-2 infection, while the use of private transportation aOR 0.56 (95% CI: 0.37-0.85) and use of a face mask aOR 0.43 (95% CI: 0.19-0.95) were associated with lower odds of infection. We identified 38 (7.7%) severe cases and 459 (92.3%) non-severe cases. Multivariate analysis identified age ≥ 50 years aOR 4.54 (95% CI: 1.86-11.08), male sex aOR 2.95 (95% CI: 1.07-8.11), hypertension aOR 3.52 (95% CI: 1.46-8.50), and diabetes aOR 5.76 (95% CI: 2.01-16.50) as risk factors for severe disease, while Hausa ethnicity aOR 0.15 (95% CI: 0.04-0.62) lowered the odds of severe disease. CONCLUSION: our findings highlight the importance of exposure history, mass gatherings, private transportation, and the use of face masks. Being over 50 years, male and having comorbidities indicate a worse prognosis.