The unnamed individual and four close contacts – two players and two members of staff - are now isolating.
The Lions say tonight’s match against the Sharks in Johannesburg will still go ahead, but the kick-off has been pushed back an hour, to 7pm BST.
The news is another blow for the tour, coming less than 24 hours after the Lions’ match against the Bulls, scheduled to take place in Pretoria on Saturday, was postponed due to a Covid outbreak in the Bulls squad.
The South Africa national side have also been badly hit and their match against Georgia on Friday has been cancelled due to a spate of Covid positives in both camps.
The Lions are due to play South Africa in Cape Town on July 24 in the first of three Test matches against the world champions.
The wisdom of undertaking the tour is now being questioned as the delta variant continues to hit South Africa hard, with health services stretched to breaking point as a third wave of infections courses through a largely unvaccinated population.
The Lions said in a statement: “The British and Irish Lions can confirm that a member of its management team has tested positive for Covid-19 following a lateral flow test as part of the Tour screening programme which took place on Wednesday 7 July.
“The individual and four close contacts – including two players and two members of staff – are being isolated and assessed at the team hotel. All members of the touring party have since been PCR tested.
“This evening’s game against the Cell C Sharks at Emirates Airline Park will still take place provided the subsequent round of PCR testing returns negative results later this afternoon. “Should this be the case, the kick-off time for tonight’s game will be adjusted to 8pm (SAST) / 7pm (BST).”
The Lions say they have been rigorous in their application of Covid protocols.
Ben Calveley, the managing director for the British and Irish Lions, said: “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
“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.
“Further updates will follow in due course.”