Australia pulled out of their Test cricket tour to South Africa Tuesday citing an "unacceptable" risk to players with the coronavirus rampant in the country.
Justin Langer's men were due to play three Tests against the Proteas, and Australia named their squad last week with the intent to fly out this month.
But the situation became untenable with the outbreak in South Africa accelerated by a new variant said to be more contagious than earlier strains of the virus.
With almost 1.5 million detected infections and more than 44,000 fatalities, it has the highest number of cases and deaths on the continent.
Cricket Australia interim chief Nick Hockley said the medical advice was not to travel.
"It has become clear that travelling from Australia to South Africa at this current time poses an unacceptable level of health and safety risk to our players, support staff and the community," he said.
"This decision has not been made lightly and we are extremely disappointed, especially given the importance of continuing international cricket at this time.
"However, we have been consistent since the start of the pandemic that the health and safety of our people is always our number one priority and unfortunately despite best efforts to agree a biosecurity plan, the risks are simply too great at this time."
The decision almost certainly ends Australia's hopes of playing in the World Test Championship final, a stated goal of captain Tim Paine.
They are currently sitting third behind India and New Zealand.
South Africa's President Cyril Ramaphosa on Monday said the country had "passed the peak" of its second coronavirus infection wave, but the virus remains a major problem.
Authorities are planning to vaccinate at least 67 percent of the population by year's end.
There are currently no contingencies in place for the tour, although Hockley suggested the Tests could be played at a later date.
"We look forward to playing the series against CSA at a date to be confirmed in due course," he said.
The tour was originally scheduled for February and March.
It is the second major tour of South Africa to be cancelled in recent months after England pulled out of their trip midway through a one-day series in December over a Covid-19 outbreak among its touring party.
It is also the second men's Test tour Australia have postponed in the last 12 months after cancelling a trip to Bangladesh last year.
Australian Cricketers' Association interim chief Joe Connellan backed Hockley's decision.
"The Australian players were ready for the contest with South Africa, especially to support South African cricket at this time with the added challenge of making the final of the ICC Test Championship," he said.
"But this is the right call given the Covid data coming out of South Africa."