Interactions between SARS-CoV-2 and influenza, and the impact of coinfection on disease severity: a test-negative design.
Int J Epidemiol 2021;
50:1124-1133. [PMID:
33942104 PMCID:
PMC8135706 DOI:
10.1093/ije/dyab081]
[Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2021] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND
The impact of SARS-CoV-2 alongside influenza is a major concern in the northern hemisphere as winter approaches.
METHODS
Test data for influenza and SARS-CoV-2 from national surveillance systems between 20 January 2020 and 25 April 2020 were used to estimate influenza infection on the risk of SARS-CoV-2 infection. A test-negative design was used to assess the odds of SARS-CoV-2 in those who tested positive for influenza compared with those who tested negative. The severity of SARS-CoV-2 was also assessed using univariable and multivariable analyses.
RESULTS
The risk of testing positive for SARS-CoV-2 was 58% lower among influenza-positive cases and patients with a coinfection had a risk of death of 5.92 (95% confidence interval: 3.21-10.91) times greater than among those with neither influenza nor SARS-CoV-2. The odds of ventilator use or death and intensive care unit admission or death were greatest among coinfected patients.
CONCLUSIONS
Coinfection of these viruses could have a significant impact on morbidity, mortality and health-service demand.
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