To analyze the differences in etiology surveillance results of influenza before and after the COVID-19 outbreak, and to provide scientific basis for influenza prevention and control under the COVID-19 epidemic.

The nasopharyngeal swabs of influenza-like cases before (2018, 2019) and after (2020, 2021) the outbreak of COVID-19 at Nantong First People’s Hospital were collected for nucleic acid testing by RT-PCR. Descriptive epidemiology was used to compare the epidemic characteristics of influenza pathogens before and after the COVID-19 outbreak.

A total of 4 181 samples were collected before and after the COVID-19 outbreak, and 405 samples were tested positive for influenza virus, with a positive rate of 9.69%, and the positive detection rate was statistically significant (χ²=91.65, P<0.001). Before and after the COVID-19 outbreak, influenza was mainly prevalent in winter and spring, and the positive rate decreased in each season after the COVID-19 outbreak. After the COVID-19 outbreak, the positive detection rate was statistically significant between the different gender (χ²=6.60, P<0.05). Between the different age groups, the positive detection rate was statistically significant except 5-14 (χ²=2.21, P>0.05). Before the COVID-19 outbreak, various types of influenza were spread alternately, and the BV type occurred after the outbreak.

The strict prevention and control measures can effectively contain the spread of influenza virus, and the positive rate and detection rate of influenza virus decreases significantly. During the new coronavirus epidemic, we should focus on the BV type of influenza and the spread of influenza among school students.