Introduction
Viral community-acquired pneumonia (CAP) is the leading source of significant morbidity and mortality worldwide [1]. The availability of multiplex molecular-diagnostic techniques has revolutionized the interpretation of the role of respiratory viruses in pneumonia in adults [2]. The prevalence of viral CAP in hospitalized patients varies from 6% to 58% according to different populations and the proportion of CAP caused by respiratory virus climbs [3]. Moreover, the emergence of new viruses, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and avian influenza A, has caused serious viral pneumonia with high mortality rates [4, 5], which attaches great importance to the research of viral CAP.
Little work has been done before and it is only during the pandemic of 2009 that bacterial superinfection is highlighted as a complication of viral CAP [6]. Bacterial pneumonia complicated between 25-50% of severe patients with influenza and will be the most important pathogenic cause of patient outcome [7-9], with the mortality climbing to 50-60%, even when appropriate antibiotics have been used [10]. Furthermore, dual Aspergillus and influenza infection is emerging and 67% mortality is linked to Aspergillosis highlights the concern for viral-fungal superinfection especially in patients with severe viral infection [11-13]. However, most conclusions addressing bacterial/fungal complications are from patients with influenza pneumonia admitted to ICU[14], or have included patients without pneumonia[15] or have involved only pediatric patients[16], or from immunocompromised patients with CAP[17], all of which may lead to significant misapprehension about the impact of superinfection on the overall population of patients with viral CAP. A recent multicenter study demonstrated that complications were common in patients with non-influenza viral pneumonia and the impact of non-influenza viruses on clinical outcomes was comparable with that of influenza virus in immunocompetent adult patients [18]. It is unclear whether the risk of superinfection of non-influenza pneumonia is similar to that of influenza pneumonia, especially for SARS-CoV-2. There is also a dearth of clinical data to figure out the potential impact of superinfection on the outcome of patients with viral CAP [6].
Early implementation of treatments to limit the possibility of superinfection may reduce the mortality of patients with influenza and delaying antimicrobial medication could be associated with higher mortality [19]. Conversely, previous studies have also shown that in-hospital all-cause mortality is significantly higher among patients who continue to receive antibiotics after viral respiratory infection diagnosis without bacterial infection [20], and overuse of antibiotics is associated with the emergence of antibiotic-resistant pathogens [20], makes patients with influenza prone toAspergillus infection [13]. Therefore, deciding who should be treated for bacterial/fungal superinfections has been the focus of considerable effort for hospitalized individuals with viral pneumonia [21]. Although a variety of factors such as mechanical ventilation, ICU admission, cardiovascular disease, older age, lymphocyte count have identified as the risk factors for the development of superinfection in patients with influenza [10, 22], there are few studies for patients with viral CAP, not merely with influenza, at an early stage.
In this study, we conducted a 2-year observational study to investigate the incidence and impact of bacterial/fungal complications in patients hospitalized with viral pneumonia and to identify predictors for the development of superinfection at an early stage.