There would probably be signs beyond North Korea's borders if there were a sudden collapse in Kim's health.
China could tighten security along its frontier to prepare for potential instability or refugee flows. Activity around North Korean diplomatic missions might also increase. Defectors in South Korea often receive information through informal networks along the Chinese border. None of this has happened.
South Korean intelligence officials, meanwhile, told Yonhap they had heard nothing to support the reports.
The rumour also echoes previous false alarms.
In 2020, a high-profile North Korean defector claimed he was "99% certain" Kim had died following cardiovascular surgery. Not long afterwards, Kim appeared in public and the claim unravelled.
So why do these rumours keep resurfacing? The first reason is succession.
North Korea has been ruled by the Kim family for three generations, but what happens after Kim Jong Un remains less certain than it was for his predecessors.
Kim Il Sung spent decades preparing his son, Kim Jong Il, for power. By the time Kim Il Sung died in 1994, the succession plan was firmly established. Kim Jong Il's transition was relatively smooth.
Kim Jong Un's rise was faster and more precarious. After Kim Jong Il suffered a stroke in 2008, his youngest son was rapidly promoted through the ranks. By the time his father died in 2011, he had been publicly identified as the future leader.
Even so, Kim Jong Un spent years consolidating power, purging rivals and eliminating perceived threats.
Today, South Korea's intelligence agency believes he may be preparing his daughter as a successor. She has increasingly appeared at high-profile events and military displays.
But she is thought to be only 13 years old. North Korea has never been led by a woman, and she has not been formally designated as heir. Her youth would also leave her vulnerable in any power struggle.
All of this uncertainty helps explain why rumours about Kim's health attract so much attention.
English (US) · 
Turkish (TR) · 