You impose a lockdown. With people confined indoors, shops close and the economy grinds to a halt. Your Covid-19 infections fall to pleasing numbers, and soon it appears safe to end the lockdown and reopen your economy. Businesses open, people come out in droves and some sense of normalcy returns.
Before you know it, new virus outbreaks emerge and clusters expand and spread, threatening to overwhelm your health care services. You impose a lockdown, rinse and repeat.