The Prevalence and Clinical Features of Co-Infection with SARS-CoV-2 and Influenza Virus during the COVID-19 Pandemic in Semnan, Iran.

Background: COVID-19 and influenza are both contagious respiratory diseases. Influenza virus can increase the severity of COVID-19 infection in the cold months of the year through damage to respiratory ciliated cells, which may cause an increase in hospitalization, disease symptoms and mortality rate. Therefore, the purpose of this study was to ascertain the frequency of co-infection with the influenza virus and SARS-CoV-2, as well as the impact of co-infection on clinical outcomes in hospitalized patients suffering from respiratory problems within Semnan City, Iran. Methods: In this cross-sectional descriptive study, we investigated 1267 hospitalized patients with respiratory problems between September 2021 and March 2022. Two nasopharyngeal and oropharyngeal throat swab samples were collected from each patient and tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A, and influenza B viruses using real-time reverse-transcriptase- polymerase-chain-reaction (RT-PCR). The collected data were analyzed with χ² test, ANOVA, paired Student's t-test, and Pearson's correlation coefficient test in different groups. Analyzes were done with SPSS 26.0 software. Results: In total, 29.6% (n = 375) of patients had confirmed positive results for SARS-CoV-2, and their median age was 55.4 ± 24.63 years. It was found that 1.9% (n = 7) and 0.5% (n = 2) of COVID-19 patients had co-infections with influenza viruses A and B, respectively. In 2.4% of the cases, co-infection with COVID-19 and influenza was found. 8 out of 9 patients (88.8%) recovered, while one patient (11.1%) died. Co-infection did not significantly correlate with cancer ( Conclusion: Although a low proportion of COVID-19 patients have influenza co-infection, the importance of such co-infection, especially in high-risk individuals and the elderly, cannot be ignored. Given the prevalence of influenza co-infection, increased coverage of flu vaccination is encouraged to mitigate the transmission of the influenza virus during the ongoing COVID-19 pandemic and reduce the risk of severe outcomes and mortality.