Epidemiological characteristics of respiratory syncytial virus in children during 2021-2024

Since the autumn of 2023, there has been a notable increase in the incidence of respiratory syncytial virus (RSV) infection among children. This study aimed to demonstrate epidemiology characteristics of RSV during and after the implementation of NPIs and to characterize the seasonal patterns of RSV following the implementation of NPIs.

This hospital-based retrospective observational study was conducted at Henan Children's Hospital. Demographic information (including gender, age, address), RSV laboratory test results, clinical severity of inpatients and outpatients enrolled during 2021-2024 were extracted from electronic medical records of the hospital. The Chi-square test was used to compare the characteristics of RSV infection.

A total of 133156 patients included in the study and 7585 of them were positive in RSV test, Throughout the whole study years, the differences in the distribution of positive rates among different years were statistically significant (χ²= 1860.490, p < 0.001). The positive rate in 2023 was the highest (9.09%), and that in 2021 was the lowest (2.17%). From January 2021 to March 2023, the positivity rate showed a downward trend, and it began to rise in April 2023, sharply increasing in November and reaching its peak in December. From April 2024 until December, the infection rate remained at a low level. However, it increased again in December. There were differences in the positivity rates among different seasons, and these differences were statistically significant (χ² = 4112.179^,p < 0.001). During the period from 2021 to 2024, the positive rate in winter was higher than that in other seasons. The positive rates for males were higher than that for females, and the differences were statistically significant (χ²= 49.678, p < 0.001). There were differences in the distribution of RSV positive rates among different age groups, and these differences were statistically significant (χ²= 863.334, p < 0.001). In 2021 and 2022, the positive rate of RSV was the highest in the 3-6 years old group, which was 3.24% and 3.49% respectively; in 2023 and 2024, the positive rate of RSV was the highest in the 0-1 years old group, which was 15.29% and 14.05% respectively.

No change in the infection patterns was observed, the RSV positive rate still peaks in winter. since 2023, there has been a trend of RSV infections shifting toward younger children. It is essential for clinicians to prioritize the prevention of RSV infection in infants.