In early 2019, Erasmus was diagnosed with microscopic polyangiitis with granulomatosis and underwent chemotherapy before and during the World Cup.
Erasmus' doctor Johan Theron told Afrikaans publication Rapport that the side effects made the coach weaker, but was essential as the disease was potentially fatal.
"He really doubted at one stage whether he would be able to push through with his position as Springbok coach," Theron said.
His chemotherapy doses were lowered so that he could give his full attention to the Springboks during the World Cup.