The Centers for Disease Control and Prevention raised its travel advisory for South Korea to its highest level after the number of confirmed coronavirus cases in the country surged past 800.

The Level 3 warning means Americans should avoid all nonessential travel to South Korea, which has the highest concentration of coronavirus infections outside China. South Korean officials say 893 people have tested positive for the novel virus.

In the United States, an additional 18 people tested positive for the coronavirus, the CDC said Monday, bringing the total number of confirmed U.S. cases to 53.

Even as cases tick upward globally, the World Health Organization declined to declare the outbreak a pandemic Monday, saying the rapidly spreading disease has “pandemic potential” but does not yet require that designation.

China’s leaders also postponed the biggest event on their political calendar, the National People’s Congress, as the country’s battle against the virus disrupts the ruling Communist Party’s agenda and hammers the domestic economy.

In a speech to party officials Sunday, President Xi Jinping warned that the outbreak was a “crisis” that would inevitably jolt the country’s economic development, but he pledged that the disruption would be temporary and manageable.

Beijing also abruptly backtracked on an earlier announcement that it would relax travel restrictions on the coronavirus-hit city of Wuhan, amplifying concerns about the government response to the outbreak.

Meanwhile, the epidemic is surging around the world. Just four days ago, Italy had only confirmed three cases. As of Monday, it has the largest known outbreak outside Asia.

Here are the latest developments:

South Korea on Tuesday reported 60 new cases of coronavirus, bringing the country’s national tally of infected people to 893. Afghanistan reported its first case. Kuwait, Iraq and Bahrain reported new cases, as well.

Official figures released Tuesday showed there had been 508 new cases of the novel coronavirus and 71 new deaths from the outbreak in China by the end of Monday, bringing the total confirmed cases to 77,658, with a cumulative death toll of 2,663.

● WHO Director General Tedros Adhanom Ghebreyesus said officials are preparing for a potential pandemic.

U.S. and global markets are reeling amid intensifying worries over devastating and potentially lasting consequences for the world’s economy.

●● The coronavirus has arrived with force in Italy, with case numbers spiking almost hourly and the virus jumping from one region to the next across the country’s north.