The U.S. Centers for Disease Control and Prevention has raised its travel advisory for South Korea to the highest level, telling U.S. travelers to stay away from the country unless they absolutely have to go. South Korea has recorded more than 900 cases of the deadly novel coronavirus, making it the worst outbreak outside of China. South Korea and China are the only two countries that have been slapped with a Level 3 advisory by the CDC, which warns Americans to “avoid all nonessential travel” until further notice. Most of the South Korean cases are in the southern city of Daegu and have been linked to a branch of a secretive religious group. The World Health Organization warned Monday that authorities around the world need to be being doing more to prepare for a possible coronavirus pandemic after the number of global cases surged past 80,000.