South African Rugby announced on Tuesday this weekend's British and Irish Lions' match against the Bulls, scheduled for Pretoria has been postponed.
The decision about Saturday's game came after four Bulls players and an official tested positive for Covid-19.
Meanwhile, the Springboks' fixture against Georgia, scheduled for Friday, is being "reviewed" after positive Covid tests in both camps.
In a statement, SA Rugby said the Bulls-Lions match was postponed "with a view to rescheduling or to accommodate an alternative opponent".
"Four Bulls players and one member of management returned positive tests which, in combination with their close contacts, made it impossible for them to field a team, according to series safety protocols.
"Series regulations make provision for additional midweek matches to be added on agreement between the organisations."
SA Rugby revealed four members of the Georgian team as well as four more Springboks had tested positive after it was announced on Monday that lock Lood de Jager had contracted the virus.
There were also six positive cases among the Springbok management, including coach Jacques Nienaber.
The latest Springboks infected are lock Marvin Orie, centre Frans Steyn, fly-half Handre Pollard and prop Frans Malherbe.
According to SA Rugby, the medical data from the Springbok and Georgian teams will be assessed by a medical advisory group (MAG) on Wednesday morning.
"These positive results are a setback and have underlined the danger of transmissibility of the Delta variant," said SA Rugby chief executive Jurie Roux.
"The Springboks' second Test against Georgia is now in serious doubt, but we will wait for the MAG to consider the data and we will make the final decision tomorrow.
"The priority is to maintain the integrity of the Test series and we will continue to focus on that."
The Lions' match against the Sharks in Johannesburg on Wednesday is still scheduled to take place.
Johannesburg and Pretoria are situated in the Gauteng province, the epicentre of the third wave of coronavirus in South Africa.
By late-Monday, there had been 2,075,409 recorded cases and 62,171 deaths in the African country most affected by the pandemic.