Leach has not been available for selection since arriving on tour and will return home before the last two Tests of the series to complete his recovery.
The left-arm spinner was hospitalised during the previous series in New Zealand and the England and Wales Cricket Board have revealed for the first time that he was suffering from sepsis, an immune response known as ‘blood poisoning’ that can be life-threatening in its most extreme forms.
Leach, who also suffers from Crohn’s Disease, was cleared to make the trip to South Africa but then found himself hit by bouts of flu and gastroenteritis which swept the camp last month.
The ECB said in a statement that Leach “has struggled to fully recover from sepsis he picked up during in New Zealand” and “has not been able to reach the expected levels of fitness to be considered for selection”.
Head coach Chris Silverwood wished the player well and hopes to have him back in the fold for a spin-friendly series in Sri Lanka in March. Leach’s Somerset team-mate Dom Bess – who played on loan at Yorkshire last year –played in the second Test win at Cape Town having originally arrived as cover and is in line to retain his place at Port Elizabeth.
Leach is the third player to depart a tour that has been disrupted by frequent medical bulletins, joining Rory Burns (ankle) and James Anderson (rib).
A total of 11 squad members and six backroom staff fell ill before or during the first Test in Centurion.
South Africa, meanwhile, could be ready to welcome AB De Villiers back from retirement, with assistant coach Enoch Nkwe claiming the star batsman’s experience would be a welcome boost for the team.
De Villiers, 35, retired from Proteas duty in 2018 but remains one of the world’s most exhilarating players.
He was reportedly keen to make his comeback during last year’s World Cup in England but could not come to an agreement with the team management.
There has since been an overhaul behind the scenes at Cricket South Africa, with De Villiers’s former team-mates Graeme Smith and Mark Boucher installed as director of cricket and head coach.
Speaking while on duty for Brisbane Heat in the Big Bash League, De Villiers hinted that he would be prepared to return, possibly for the Twenty20 World Cup in October and this time the reception might be more enthusiastic.
“Maybe it is something that is happening behind the scenes. If he was to be approached or if he was to show some interest...I know for sure he’d be someone who would consider it,” said Nkwe.
“You have to earn it, it’s not just walking into the team. AB has commitment to South African cricket. He has been involved in the Mzansi Super League and I’m sure if he shows interest, he’ll be involved in some of the series we’ll be playing (before the WT20). We’ll wait and see if he’s interested or not.
“But it’s always good to have some sort of experience and I’m sure the life experience he’s gained from the last year or two being outside international cricket, that would be immense for the environment and South African cricket.”
The MCC Cricket committee and MCC World Cricket committee both believe Test cricket should continue to be played over five days.
The ICC has raised the idea of Tests being shortened from five days to four but the MCC has laid out their stance on the future of Test cricket.
A statement read: “MMC has noted the recent discussion regarding the future of Test cricket and the ICC’s desire to debate the introduction of four-day Test cricket to replace the current five-day format in the World Test Championship from 2023.
“The MCC Cricket committee and MCC World Cricket committee have recently discussed the issue and although they can see some benefits that four-day Test cricket could bring, both committees believe Test cricket should continue to be played over five days.”
Five-day Tests have been set since 1979 and some of the format’s most thrilling finishes – including the draw at the Oval which sealed England’s historic 2005 Ashes win and the recent win over South Africa in Cape Town - have been played out on the final day.
The ICC, however, has permitted certain Tests since 2017 to be played over four days. These matches are outside the World Test Championship, such as England’s historic meeting with Ireland at Lord’s in July.