“The medical evaluation provided to the Busch family concluded that severe pneumonia progressed into sepsis, resulting in rapid and overwhelming associated complications,” a family statement said, AFP reported.
“The family asks for continued understanding and privacy during this difficult time.”
Sepsis is when the body’s infection-fighting process turns on the body and causes organs to work improperly, which can cause severe damage and death.
Earlier this month, Busch radioed his crew near the end of a race at Watkins Glen asking for a medical “shot” after finishing, the AP reported. He had been battling a sinus cold aggravated by G-forces and elevation changes at the road course on May 10.
Busch, in his 22nd Nascar campaign, was among the top drivers in the elite division of the US stock car racing series.
His family and his Richard Childress Racing team had announced Busch’s hospitalisation and withdrawal from Sunday’s Coca-Cola 600 race Thursday morning, hours before announcing his death, AFP reported.
The race will be conducted as planned on Sunday at Charlotte Motor Speedway in North Carolina, with every car in the field bearing a number eight decal in tribute to Busch.
Nascar CEO Steve O’Donnell said Busch was not always easy to deal with but was “an American badass”, AP reported.
“We certainly had our battles but I would give a lot of money to have a few more battles,” O’Donnell said.
Former teammate Denny Hamlin wrote a tribute on social media.
“Absolutely cannot comprehend this news. We just need to think of his family during this time. We love you KB,” Hamlin wrote on X.
Busch is survived by his parents, his wife, and two young children.
Over his career, Busch won 234 races in Nascar’s top three series, more than any driver in history, according to ESPN.