The report said that April 15 was Kim's grandfather's birthday. He was absent on the occasion that day. This is why the suspicion of his condition worsening. However, he was seen at a government meeting four days ago.
The report quoted another U.S. official as saying that information about Kim's condition was "accurate." But it is very difficult to get the actual information there.
According to the South Korean-based website Daily N, Kim's health has deteriorated over the months due to smoking, obesity and overwork. Recently the leader in North Korea underwent cardiovascular surgery. After that he became seriously ill.