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Community-acquired viral respiratory infections amongst hospitalized inpatients during a COVID-19 outbreak in Singapore: co-infection and clinical outcomes

Our take —

This study was conducted at Singapore General Hospital, and assessed community-acquired coinfections for SARS-CoV-2 and other viral respiratory infections. Out of 3807 patients hospitalized, 19.3% were infected with SARS-CoV-2, and only 6 of those cases also had a viral respiratory coinfection. These data suggest co-infection among COVID-19 patients is limited, however SARS-CoV-2 coinfections may not be representative of cases not requiring hospitalization or of areas with greater seasonal viruses circulating.

Study design


Study population and setting

This study sought to estimate the prevalence and etiology of viral respiratory infections requiring hospitalization at a large, public, tertiary hospital (Singapore General Hospital). All patients presenting with respiratory symptoms or radiology of likely pneumonia from February 5 to April 15, 2020 were included in the study. Oropharyngeal or other respiratory swabs were collected within 24 hours of patient admission.

Summary of Main Findings

The rate of admission doubled over the study period, from 316 in week 1 to 659 in week 10, and for SARS-CoV-2 respiratory infections, it increased from 5 cases in week 1 to 210 cases in week 10. Among the 3807 respiratory-related admissions, 19.3% (n=736) had a viral respiratory infection from PCR analysis; 58.5% of these (n=431) were positive for SARS-CoV-2. Only 6 (1.4%) SARS-CoV-2 infected patients had coinfections. SARS-CoV-2 infected patients had lower odds of respiratory coinfection (0.27, 95% CI: 0.11 – 0.72), compared to patients with other respiratory virus. Rhinovirus was most correlated with SARS-CoV-2 infection, followed by parainfluenza.

Study Strengths

The study had multiple weeks of cross-sectional data to use for a time series for SARS-CoV-2, as well as other respiratory viruses to show the trends in SARS-CoV-2 infection compared to other viral infections. By also measuring coinfection rates, these data offer important information about the risk of coinfection in a community sample with severe illness that requires hospitalization. The study also had detailed case histories about those with SARS-CoV-2 who were infected.


This study examined infections requiring hospitalization, which may lead to selection bias for those with higher severity of disease than would exist in the population prevalence. Many of the other respiratory viruses examined have seasonal trends which could not be observed due to Singapore’s climate, so there may be reduced generalizability to other settings. Finally, SARS-CoV-2 coinfections were uncommon (n=6), and so it was not possible to test for risk factors for coinfection among those with COVID-19, and only a descriptive case history could be given.

Value added

This study is one of the few that looks at coinfection, and has a wide range of respiratory infections included with one of the largest sample sizes.

This review was posted on: 17 June 2020