The Centers for Disease Control and Prevention (CDC) warned Americans against unnecessary travel to South Korea on Monday amid growing concerns about the outbreak of a novel form of coronavirus originating from China.

A notice on the CDC’s website Monday evening urged travelers to “avoid all nonessential travel to South Korea,” citing limited access to medical services in areas where the coronavirus outbreak has been reported.

“A novel coronavirus is causing an outbreak of respiratory illness (COVID-19) in South Korea. Illness with this virus has ranged from mild to severe. Signs and symptoms of infection include fever, cough, and difficulty breathing. Sore throat also has been reported in some patients. Some patients also have reported diarrhea without other symptoms,” reads the CDC’s warning.

“This new coronavirus has caused severe disease and death in patients who developed pneumonia. Risk factors for severe illness are not yet clear, although older adults and those with chronic medical conditions may be at higher risk for severe illness,” it continues.

The number of coronavirus cases in South Korea surged to 833 on Monday, up from 602 just one day before. 

The coronavirus outbreak is believed to have begun in the Chinese city of Wuhan. Chinese officials have now reported more than 2,000 deaths across the country as tens of thousands have been stricken by the disease.

U.S. health officials have urged against travel to the affected regions and instituted medical screenings at several major U.S. airports as a handful of cases, none of them severe, have been reported in the U.S.

The majority of cases have been reported in China, Japan and South Korea, though a small number of cases in other countries throughout Asia have been reported as a result of travelers arriving from affected regions.

The CDC has also warned against travel to China and urged travelers to Japan, Iran and Italy to exercise precautions. The State Department has elevated its travel advisory for China to the highest level.