"Paul is still feeling ill and this cancellation is unavoidable," said a statement issued by Hyundai Card Co. Ltd., one of the organizers of the concert that had been slated for May 28 in Seoul.
The show would have been the 71-year-old musician's first appearance in the country.
"I was really looking forward to visiting and playing in South Korea for the first time and I'm sorry to be letting fans down," McCartney said in the statement. "I'm very disappointed by this and hope to be able to visit soon."
A spokesperson for the singer released a statement on Thursday confirming that he had been treated in a Tokyo hospital for a symptoms from the virus.
"Since contracting a virus last week that led to the postponement of tour dates, Paul received successful medical treatment at a hospital in Tokyo," the statement said. "He will make a complete recovery and has been ordered to take a few days rest. Paul has been extremely moved by all the messages and well wishes he has received from fans all over the world."
McCartney postponed May 17-18 and 21 shows in Tokyo, as well as a show he had rescheduled for May 19. His May 24 concert in Osaka and the South Korea show are now also listed as postponed on his official website. Some Beatles fan sites and blogs carried unconfirmed reports Thursday that McCartney's daughters Mary and Stella had flown to Japan to be with their father.
"Doctors have ordered Paul complete rest and he has been doing all he can to get better," read a previous statement posted on that site. "Paul has only ever had to reschedule a handful of shows in his entire career and is so upset about this situation, he hates to let people down.
"This morning he told his staff he was going to try and perform tonight against doctors' orders, but his team, along with the doctors, wouldn't allow it," the statement continued. "He has been very moved by fans' reactions and messages of love and support he has received in Japan."
In a statement attributed to McCartney, he said, "Thank you so much for your kind messages of support. I'm so very touched. Unfortunately my condition has not improved overnight. I was really hoping that I'd be feeling better today. I'm so disappointed and sorry to be letting my fans down."
The U.S. leg of his new Out There tour is scheduled to begin on June 14 in Lubbock, Texas, and includes two dates in California: Aug. 10 at