The burden, clinical features and outcomes of SARS-CoV-2, Influenza and co-infections during concurrently out-of-season outbreaks in Brazil

Abstract

Objectives: Little is known about the burden and the clinical presentation and prognosis of individuals with Influenza and SARS-CoV-2 during concurrent outbreaks. We aimed to describe the burden, clinical characteristics and outcomes of hospitalized adults during the Influenza A/H3N2 and Omicron outbreaks in Brazil.

Study design: Cross-sectional analysis of national surveillance data.

Methods: We described the health system burden and clinical features of confirmed cases of Influenza and/or SARS-CoV-2 reported in the national surveillance system during the Influenza A H3N2 out-of-season outbreak and the first Omicron surge between November 2021 and March 2022 in Brazil. A multilevel mixed-effects logistic regression model adjusted by a priori defined confounders was used to evaluate the association between the infection type and resource use and mortality.

Results: The outbreaks occurred simultaneously across all Brazilian regions. Coinfected patients had clinical features from both infections. Influenza coinfected cases had similar odds for requiring ICU admission (adjusted odds ratio, aOR 0.96, 95 % CI, 0.80-1.15, p = 0.634), mechanical ventilation (aOR 0.88, 95 % CI, 0.70-1.11, p = 0.290), and in-hospital mortality (aOR 1.02, 95 % CI, 0.84-1.23, p = 0.847) compared to COVID-19 only. Influenza had lower odds for requiring ICU admission, mechanical ventilation and in-hospital mortality compared to COVID-19 only.

Conclusions: Simultaneous surges of Influenza and SARS-CoV-2 increased the pressure on the health system of Brazil. Coinfection was not associated with higher resource use or death; Influenza was associated with better outcomes, compared to COVID-19.

Keywords: Coinfection; Covid coinfection; Covid-19; Flu; Flu outbreak; Sars-cov-2 outbreak.