As COVID-19 spreads around the world, some countries' timelines look different from others. With a combination of contact tracing, testing, and isolating cases, along with other physical distancing policies, places like South Korea were able to reduce the size of its coronavirus outbreak and flatten the curve. But many other countries have seen the number of new cases grow exponentially. Countries that didn't start testing and tracing early have had a harder time reducing the number of daily new coronavirus cases.