The British and Irish Lions' clash with the Sharks is in doubt after a member of their management team tested positive for coronavirus, while South Africa's game with Georgia is off.
Warren Gatland's men are due to face the Sharks in the second match of their tour of South Africa on Wednesday.
However, four members of the touring party, including two players, are now isolating having been deemed to be close contacts of the individual who had the positive test result.
Kick-off has been pushed back to 20:00 local time (19:00 BST) pending the results of PCR tests for the rest of the touring party. The game will go ahead should those tests return negative results.
"We have followed all necessary precautions since the start of the tour, which included regular testing and rigorous COVID-19 counter measure planning and protocols," said Ben Calveley, managing director for the Lions.
"Our priority is to ensure the health and safety of the entire touring party, which is why we quickly isolated the players and staff upon receiving the news of the positive result.
"Everyone has subsequently been lateral flow and PCR tested. The Medical Advisory Group await the results of the PCR testing in order to make a decision on tonight's game.
"The five individuals affected will be monitored closely during isolation and receive the best possible medical attention as we await the results of their PCR tests."
The Springboks' second Test with Georgia was cancelled due to COVID outbreaks in both camps.
South Africa's playing and management group returned 12 positive tests this week, with Georgia returning four.
Jurie Roux, CEO of South Africa Rugby, said: "In the context of the loss of life and economic damage that COVID and this third wave are wreaking, the cancellation of a rugby match is pretty trivial.
"But it is still a major disappointment for the many stakeholders who have invested so much time, energy and resources into making these matches happen.
"I especially feel for the fans and players, and for our visitors from Georgia who travelled here at relatively short notice to take on the series, which has now been cut short. We've not been able to interact with them because of the bio-secure environments, but I'd like to thank them publicly for their support.
"We continue to plan for the Springboks' re-emergence from isolation and the completion of the Test series but in the short term we wish a speedy recovery for those who have been infected."
The Lions' clash with the Bulls on Saturday is already off and, while they are scheduled to face South Africa 'A' next Wednesday, the remainder of the tour now looks to be in question.