Rugby: South Africa coach Rassie Erasmus was under-going chemo at Rugby World Cup

Springboks head coach Rassie Erasmus was reportedly undergoing chemotherapy during his side's triumphant campaign at the 2019 Rugby World Cup in Japan.

South Africa claimed their third World Cup title after beating England in the final but according to South African newspaper Rapport, Erasmus was facing a serious health scare at the time.

The 47-year-old, who became Springbok director of rugby after the tournament, was diagnosed with a rare autoimmune disease called microscopic polyangiitis with granulomatosis in early 2019, according to Rapport.

The disease can severely impact the lungs, kidneys, sinuses and trachea.

Although not being cancerous, Erasmus reportedly has a rare strain of the disease and it put into doubt whether he would coach at the World Cup.

New Zealand head coach Steve Hansen congratulates World Champion South African head coach Rassie Erasmus during the World Rugby Awards 2019. Photosport

According to the Rapport, Erasmus continued with the treatment until March this year and it was considered successful.