Abstract
Secondary bacterial infections are a potentially fatal complication of influenza infection. We aimed to define the impact of secondary bacterial infections on the clinical course and mortality in coronavirus disease 2019 (COVID-19) patients by comparison with influenza patients. COVID-19 (n = 642) and influenza (n = 742) patients, admitted to a large tertiary center in Israel and for whom blood or sputum culture had been taken were selected for this study. Bacterial culture results, clinical parameters, and death rates were compared. COVID-19 patients had higher rates of bacterial infections than influenza patients (12.6% vs. 8.7%). Notably, the time from admission to bacterial growth was longer in COVID-19 compared to influenza patients (4 (1–8) vs. 1 (1–3) days). Late infections (> 48 h after admission) with gram-positive bacteria were more common in COVID-19 patients (28% vs. 9.5%). Secondary infection was associated with a higher risk of death in both patient groups 2.7-fold (1.22–5.83) for COVID-19, and 3.09-fold (1.11–7.38) for Influenza). The association with death remained significant upon adjustment to age and clinical parameters in COVID-19 but not in influenza infection. Secondary bacterial infection is a notable complication associated with worse outcomes in COVID-19 than influenza patients. Careful surveillance and prompt antibiotic treatment may benefit selected patients.
Highlights
Secondary bacterial infections are a potentially fatal complication of influenza infection
Laboratory tests known to correlate with inflammation were more severe among COVID-19 patients compared to influenza patients, maximal C-reactive protein (CRP) levels (median 13.41 (IQR (6.22–24.94) vs.7.05 (3.3–15.4), p < 0.001), maximal ferritin level (743.35 (330.7–1600.5) vs. 190.20 (61.2–351.4), p < 0.001) and minimal albumin levels (3.00 (2.5- 3.5) vs. 3.5 (3.10- 4.00) p < 0.001)
Most secondary bacterial infections in both groups were derived from blood cultures
Summary
Secondary bacterial infections are a potentially fatal complication of influenza infection. Despite the clinical importance of secondary bacterial infections, their contribution to COVID-19 severity and mortality is still not well established Several studies addressed this issue, but variations in testing methodologies, site-specific nosocomial infections, different definitions of early vs late infections, and differences in treatment modalities, complicate the analysis of these data. Influenza and COVID-19 have different disease courses, with influenza having a shorter incubation time and disease duration7 These differences might reflect disparities in the magnitude and kinetics of the immune response to these pathogens, affecting the type and time of the appearance of secondary bacterial infections, as well. We compared early (< 48 h after admission) or late (> 48 h after admission) secondary bacterial infections identified in blood or sputum cultures of admitted influenza or COVID-19 patients from a single large tertiary center in Israel
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