Outbreak of Influenza and Other Respiratory Viruses in Hospitalized Patients Alongside the SARS-CoV-2 Pandemic

Abstract

Influenza A and other respiratory viruses, circulate each winter and cause respiratory illness that can lead to severe complications in hospitalized patients. During the COVID-19 pandemic, only a few cases of respiratory viruses were detected in Israel. Our study applied RT-PCR to examine 13,674 samples collected from patients hospitalized with respiratory symptoms in 2019, 2020, and 2021 and the first half of the 2022 winter. A sharp increase in influenza A(H3N2) cases was observed in winter 2021-2022 as compared to 2020, followed by a sudden decrease in influenza cases after the detection of the SARS-CoV-2 omicron variant in Israel. Comparison of the area under the curve (AUC) of influenza infection rates during 7 consecutive winter seasons found that the minimal AUC between 2015 and 2020 was 281.1, while in 2021-2022, it was significantly lower (162.6 AUC; p = 0.0017), although the percentage of positive influenza cases was similar to those of previous years. The presented findings show how the dominance of influenza A(H3N2) abruptly ended upon circulation of the SARS-CoV-2 omicron variant. However, a post-COVID-19 influenza outbreak is possible, hence the planning of the next influenza vaccine is critical to ensure lower influenza-related hospitalization rates.

Increased detection of Echovirus 6-associated meningitis in patients hospitalized during the COVID-19 pandemic, Israel 2021–2022

“…Person-to-person infection results from the introduction of the infected stool/mucus into an uninfected person through the oral cavity. This assumption coincides with reports of other respiratory viruses [ 20 , 21 ] that were attenuated during the pandemic.…”

Omicron‐induced interferon signaling prevents influenza A H1N1 and H5N1 virus infection

“…17 The BA.1-and BA.5-induced interferon responses generated an antiviral state that protected infected cells from super-infection with influenza A viruses, showing that the Omicron-induced interferon response is of functional relevance. Our analysis of the spread of influenza-like illnesses during the Delta and BA.1 infection waves (Figure S6) and a number of additional studies [31][32][33][34][35] suggest that Omicron may interfere with influenza A virus transmission. However, these are correlations that need to be considered with care, and a causative relationship remains to be established.…”

“…Similarly, three further studies reported a decrease of influenza A virus infections when the Delta variant was replaced by the Omicron variant. [31][32][33] Additional studies found that Omicron patients were less likely to be coinfected with influenza A viruses than Delta patients 34 and that an H3N2 outbreak in Brazil only occurred after a decline in Omicron cases. 35 Notably, such observations do not provide conclusive evidence on a potential impact of Omicron circulation on influenza A virus spread.…”

Prevalence of Respiratory Viral Infections in Deceased Persons during the COVID-19 Pandemic Season 2021–2022: A Population-Based Observational Study

“…Non-pharmacological preventive measures that had been applied during the COVID-19 pandemic were relaxed in the 2021–2022 season, resulting in an intense circulation of SARS-CoV-2 [ 20 , 21 ], and this virus displaced other respiratory viruses like influenza or RSV, which circulated scarcely [ 7 , 8 , 16 , 22 ]. Similarly, SARS-CoV-2 was the more frequent virus detected among deceased persons.…”