Fig. 4.

Forecasting H1N1 or H3N2 influenza trends in mainland China using the SARIMA model. The graphs display the predicted transmission of either H1N1 (left) or H3N2 (right) influenza in North or South China from 2018–2023. The blue line represents the South cities, while the orange line for the North cities. A gray dashed line is used to indicate the boundary for each year, with the gray-shaded region indicating the NPIs period, the red region representing the transitional period after NPI relaxation, and the yellow region illustrating the SARIMA model’s predicted trend for the next 3 years