You can thank 3 countries and 3 countries only for the record number of cases: Russia, Brazil and USA.
Also, there is absolutely no script saying there will be a second wave. It's a huge possibility, but who says the virus is going to mutate? What a big conspiracy theory and I hear it a lot as if it's part of a script or if its "Spanish Flu rewritten". This isn't a written story folks. No one knows what's going to happen next.
Also, South Korea and China didn't have second waves. They both had a small second outbreak in certain cities. South Korea thanks to that night club fiasco and China due to Russians entering a city (not sure about the name) with the virus. Otherwise, there's not been anything.