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

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.