Explain what type of Time Series Methodology (Retrospective/Prospective-Mixed Method) is most appropriate to best predict how the Curve can be Flattened?

Please read the following article on Flattening the Curve.
https://www.washingtonpost.com/graphics/2020/world/corona-simulator/
Explain what type of Time Series Methodology (Retrospective/Prospective-Mixed Method) is most appropriate to best predict how the Curve can be Flattened?