Background: Following the Coronavirus disease (COVID-19) pandemic, new changes in the transmission of various pathogens have occurred. The environmental changes influenced by the COVID-19 pandemic have affected the flow of human society and the survival environment of other microorganisms. The prevalence of influenza viruses has also changed under this selection pressure. Objective: To investigate the influenza virus’s prevalence, risk factors and symptom characteristics during the outbreak of COVID-19. Methods: Samples and data were collected from outpatients requiring respiratory virus tests in a tertiary hospital. Throat swabs were tested in the immunocolloidal gold method. Characteristics of influenza A and B compared before and after the outbreak of COVID-19. Results: The dominant virus strain in 2020-2022 has gradually changed from influenza A to influenza B. Influenza A is mainly prevalent in 0 to 20 years old (P < 0.05), and influenza B is dominant in all age groups. Most of the patients with positive results were from paediatrics and presented in fever clinics (P < 0.05); Most of the patients were diagnosed with fever and upper respiratory tract infection (P < 0.05). Conclusion: The influenza virus’s positive rate, risk factors and symptom characteristics have changed compared to previous years. It means the epidemic prevention measures have greatly affected the prevalence of the influenza virus since the outbreak of COVID-19.

Background: Following the Coronavirus disease (COVID-19) pandemic, new changes in the transmission of various pathogens have occurred. The environmental changes influenced by the COVID-19 pandemic have affected the flow of human society and the survival environment of other microorganisms. The prevalence of influenza viruses has also changed under this selection pressure. Objective: To investigate the influenza virus’s prevalence, risk factors and symptom characteristics during the outbreak of COVID-19. Methods: Samples and data were collected from outpatients requiring respiratory virus tests in a tertiary hospital. Throat swabs were tested in the immunocolloidal gold method. Characteristics of influenza A and B compared before and after the outbreak of COVID-19. Results: The dominant virus strain in 2020-2022 has gradually changed from influenza A to influenza B. Influenza A is mainly prevalent in 0 to 20 years old (P < 0.05), and influenza B is dominant in all age groups. Most of the patients with positive results were from paediatrics and presented in fever clinics (P < 0.05); Most of the patients were diagnosed with fever and upper respiratory tract infection (P < 0.05). Conclusion: The influenza virus’s positive rate, risk factors and symptom characteristics have changed compared to previous years. It means the epidemic prevention measures have greatly affected the prevalence of the influenza virus since the outbreak of COVID-19.