again: the spanish flu mutated. twice.

that's why there were waves.

will there be multiple waves of this, too?

if it mutates a couple times, you should expect that, yes. and, over time, because it's not going away, you would expect it to become seasonal - which is what happened to the spanish flu.

if it's very slow to mutate, the difference between a "wave" and a "season" will likely get blurry.

https://www.ctvnews.ca/health/coronavirus/coronavirus-is-one-big-wave-not-seasonal-who-expert-suggests-1.5044839