Spain and Italy have both held the titles of "healthiest country in the world" in recent years.

All three have incidence rates more than an order of magnitude larger than South Korea.

Wearing respiratory protection equipment protects against respiratory contaminants. Testing people and tracing contacts helps to contain outbreaks. The answer is really that simple. South Korea was one of (if not) the first countries to start an aggressive testing and tracing program.

On TV, I watched their citizens line up in cars at mass testing sites months before my multi-billion-dollar healthcare conglomerate here in the US even had testing available at all.