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. 2025 Jun 16;17(6):851.
doi: 10.3390/v17060851.

The Effect on Mortality of Bacterial Co-Infections on Critically Ill Patients with Community-Acquired COVID-19 and Influenza Pneumonia: A Systematic Review

Apostolos A Menis  1 , Efrosyni Gerovasileiou  1 , Konstantinos Mantzarlis  1 , Efstratios Manoulakas  1 , Konstantina Deskata  1 , Vasileios Vazgiourakis  1 , Demosthenes Makris  1 , George Dimopoulos  2
Affiliations

The Effect on Mortality of Bacterial Co-Infections on Critically Ill Patients with Community-Acquired COVID-19 and Influenza Pneumonia: A Systematic Review

Apostolos A Menis et al. Viruses. .

Abstract

Background: Bacterial co-infections in patients with viral pneumonia might increase mortality. In this study we aimed to evaluate their effect on the mortality of critically ill patients with viral pneumonia. Methods: A systematic search was conducted in PubMed, Web of Science, Scopus and Cochrane from inception until 30 March 2025. We included studies comparing the effect on mortality of bacterial co-infections in critically ill patients with viral pneumonia. The risk of bias was assessed by the Newcastle-Ottawa Scale. Results: From 3643 studies, 10 were included in our study with a total of 2862 COVID-19 patients and 4573 influenza patients. Seven studies were retrospective and three prospective. In total, 359/2862 of the COVID-19 and 904/4573 of the influenza patients were co-infected. Co-infections increased mortality in five out of the six studies evaluating COVID-19 patients and in two out of the eight studies evaluating influenza patients. Conclusions: The majority of the included studies were retrospective, which may limit the accuracy of these results. The exclusion of non-English literature may have led to the omission of relevant data. Based on our results, the impact of bacterial co-infection may be more pronounced in patients with COVID-19 pneumonia admitted to the ICU than in patients with influenza pneumonia.

Keywords: co-infection; critical care; mortality; pneumonia; virus.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Flow chart of the study selection.
Figure 2
Figure 2
Forest plot displaying the odds ratios (ORs) and 95% confidence intervals (CIs) for mortality associated with bacterial co-infection in individual studies of critically ill patients with COVID-19. No pooled effect estimate was calculated; the plot is presented for descriptive purposes only. Odds ratios are shown on a logarithmic scale [43,44,47,48,49,50].
Figure 3
Figure 3
Forest plot displaying the odds ratios (ORs) and 95% confidence intervals (CIs) for mortality associated with bacterial co-infection in individual studies of critically ill patients with influenza. No pooled effect estimate was calculated; the plot is presented for descriptive purposes only. Odds ratios are shown on a logarithmic scale [43,45,46,47,49,51,52].
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