Influenza incidence overlapped with COVID-19 or under COVID-19 control measures.

INTRODUCTION

COVID-19 pandemic caused infection when influenza was still prevalent. This study was conducted to examine influenza incidence overlapped with COVID-19 and the effect of the COVID-19 measures on influenza incidence as a proxy.

METHODS

The routine sentinel surveillance data on COVID-19 and influenza was obtained from the national integrated care electronic health record system. Data were collected in 28 points from 11 months before the outbreak (from March 2019 to January 2020) and 17 months after the outbreak (February 2020 to June 2021).

RESULTS

In Iran, the incidence rate of influenza was 51.1 cases per 100,000 populations in November 2019, while it was only 0.1 in November 2020. The average number of influenza cases specifically for the Kurdistan province during the seasonal flu peak in 2019-2020 was 2.5 cases per 100,000 populations, while the average of influenza cases in the preceding 4 years was 0.4 cases per 100,000 populations. In other words, the seasonal peak of influenza in Iran was significantly higher than that of previous and after years.

CONCLUSION

It seems that some of the nonpharmaceutical interventions (NPIs) used to control COVID-19 are effective against influenza epidemics and the results indicated a marked decline in the number of influenza cases may cause after the implementation of public health measures for COVID-19. The results showed the seasonal peak of influenza in Iran was significantly higher than that of previous years, so it seems that the influenza winter peak season (November 2019) overlapped with SARS-CoV-2 causing observed undetected infection during influenza winter peak.