Fig. 6.

The predictions of year effect on the weeks of the average percentage of respiratory virus antigen tests positive for RSV per week in 2013–2022, as obtained from the non-linear ordinary least squares regression model. The graph begins at calendar week 27. Season onset and offset are indicated by the 2 orange vertical lines. The non-linear ordinary least squares regression model indicated that the year effect on the weeks of epidemic clusters was statistically significant (P-value < 0.001, Fig. 6). Thus, the epidemic season has changed. RSV activity in 2020–2021, resurgence during the summer and autumn, started earlier by 12 weeks when compared with the predictions of year, peaked later (the 7 week), and lasted longer. RSV activity in 2021–2022, started earlier by 18 weeks when compared with the predictions of year, peaked and offset within the predicted range