To analyze the epidemic characteristics of influenza-like cases, the composition and changes of pathogen spectrum and the use of antiviral drugs in Beijing Haidian Hospital during influenza season (December to February of each year) from 2017 to 2019, and to provide a basis for the prevention and treatment strategy of influenza-like cases.

The information and laboratory pathogen monitoring results of influenza-like cases reported in the fever outpatient clinic, emergency department and pediatric emergency department of Beijing Haidian Hospital from 2017 to 2019 were collected, retrospectively. The epidemic intensity, pathogen composition and antiviral use of influenza-like cases were analyzed by descriptive epidemiological method. The reports of influenza-like cases and the use of antiviral drugs in different years and age groups were compared and analyzed, respectively.

In 2017-2018, 78.6% of patients receiving antiviral treatment were positive for influenza virus antigen, while in 2018-2019, the proportion decreased to 52.4%. In 2017-2018, compared with other age group, the proportion of positive influenza virus antigens in the group > 25 years old was relatively low, with significant difference (χ² = 254.398, P < 0.001), and the proportions of positive influenza virus antigens in the group > 60 years old was significantly low in 2018-2019, with significant difference (χ² = 668.543, P < 0.001). In both 2017-2018 and 2018-2019, the proportions of positive influenza virus antigens in December was significantly high, with significant differences (χ² = 232.397, P < 0.001; χ² = 212.497, P < 0.001). Influenza B were the dominant antigen type in 2017-2018, and influenza A was the dominant antigen type in 2018-2019, with significant differences (χ² = 74.545, P < 0.001; χ² = 187.847, P < 0.001). The proportion of influenza-like cases receiving antiviral therapy increased from 38.9% in 2017-2018 to 64.6% in 2018-2019. The proportion of antiviral therapy in age groups of < 4 years old and > 60 years old were low, and the antiviral therapy rates in the two groups were 22.2% (937/4 221) and 30.1% (575/1 908) in 2017-2018, respectively, with significant difference (χ² = 1 210.409, P < 0.001). The antiviral therapy rate in the two groups were 40.0% (1 185/2 964) and 46.1% (767/1 665) in 2018-2019, respectively, with significant difference (χ² = 1 850.166, P < 0.001).

The proportion of influenza virus antigen positive was higher in December. Influenza B was the dominant antigen type in 2017-2018, and influenza A was the dominant antigen type in 2018-2019. The anti-virus therapy of influenza-like children under 4 years old and the elder people over 60 years old were still with low proportion and needs to be furtherly improved.