Fig. 3

Trend change analysis of relative search volume on Google Trends and sentinel surveillance data between 2018 and 2021 using Joinpoint regression. Three Joinpoints were established and evaluated to determine whether any significant change points occurred between each period. The relative search volume on Google Trends and the sentinel surveillance data for 2018 (a, b), 2019 (c, d), 2020 (e, f), and 2021 (g, h) are shown. The blue, green, red, and light blue line indicates period 1, 2, 3, and 4, respectively. In graphs a, b, c, d, and g, the change- points between the blue and green lines indicate the start of a RSV epidemic. In the graph h, the start of a RSV epidemic appears as a change-point between the green and red lines