The risk of matches being cancelled if a squad returns too many cases of Covid-19 remains real as the South African summer gets underway on Friday.

The hosts have already been hit with two positive tests and have since been tested twice more, including a final round on Thursday morning. Their third test run revealed no new cases.

Asked what would happen if the pre-match tests showed a significant number of cases, CSA's chief medical officer, Dr Shuaib Manjra explained it could impact the schedule.

"There probably won't be a game. If you've got lots of positives you've got a quarantine context," he said. "We cannot bring in a player from the outside without testing them at least twice before we bring them into this space. If a large group of people test positive we wouldn't have adequate opportunity to bridge people into the bio-bubble. But we've got a squad of 24 so hopefully we can put a team together."

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This is South Africa's first experience of operating in a bio-secure environment as a national team (although several players have just returned from 11 weeks of doing it in the IPL) and will become their new-normal for the next six months. In a country where healthcare resources are challenged and where, as of this week, overall Coronavirus case numbers are going up, South African cricket will have to learn to box clever in the environment and with the welfare of their players, making this the most complicated season yet.

Ahead of this series, the 24 players were tested before entering their base and one returned a positive result. He was kept out of the bubble and quarantined at a different venue. Two other players who were deemed to have come in close contact with the player were isolated and have since tested negative. A second player then tested positive a few days later, having already been in the bubble, and had to be removed. Both players will be retested and if negative, will rejoin the squad on Saturday, ending a tough period for both of them.

"The players were devastated on receiving the news that they had tested positive for Covid," Manjra said. "He (the first player) has taken quite a bit of strain in the sense that he's been isolated in a hotel all alone and not participating in training.

"There's going to be a lag period in him coming to the squad and getting back to fitness because of injury concerns. If you've been in a hotel room for 10 days we can't simply throw you onto the park. We've got to give at least another seven days to return to match fitness in order to consider him for any of the games. It takes a mental toll on him and all the others."

Manja described the period around testing as "stressful," and the tests themselves as "uncomfortable," but unavoidable. "Players don't like the Covid test. We had a guy here doing the test on Monday and the players complained, so we had to try and get somebody else. Some of them are over enthusiastic, and not only get into your nose but into your sinuses and into your brain as well," Manjra said. "It's an uncomfortable test, but it's very short."

And it will have to happen continuously as the summer goes on. Testing will be done again between the T20s and ODIs "to ensure the integrity of the bubble is maintained," and before each Test match. South Africa have five scheduled for the summer.

"Building resilience is not about removing distractions. It's how you deal with those distractions, which will always be there." Dr Shuaib Manjra, CSA's chief medical officer

During the period in which they are in the bubble, players will have to continue to operate in small groups, whether at training or socially. "In the event that somebody tests positive we isolate a small group of people rather than the entire contact or non-contact group. That has a role to play in the dynamic of the team in terms of training, dining and socialising," Manjra said.

Those limitations, the administrative crises at CSA and the controversy over the way South African cricket has handled the Black Lives Movement have all made for an imperfect build up to the series but, Manjra believes, helped them become closer as a squad.

"Preparing without distractions is an ideal situation, but in the real world you always have distractions. One of the things that allowed our team to build resilience is much of the kind work we're doing in the background with the squad," he said. "There's a lot of opportunity during lockdown for the players to interact with each other and get to know each other, and play out some of the dynamics we've been speaking about.

"For us it's not only about symbolism but about living particular experiences and sharing them -- demonstrating what we believe in. The lockdown has a positive effect in those terms. Building resilience is not about removing distractions. It's how you deal with those distractions, which will always be there."

Eoin Morgan, the England captain, was understanding of the challenges of keeping the sport's bio-secure environments safe.

"During the summer we did a magnificent job in not having any cases at all," Morgan said. "We felt in a very privileged position, not to have to worry about the virus in our bubble, but this has presented different challenges.

"South Africa have had two cases. One was off site, one was on the site, at the hotel, which presented a different challenge. To us, very similarly in the summer, if we had a case, we needed to be able to demonstrate that we could contain it to make every team, and every player within that bubble secure and safe, and South Africa seem to have done that so far."

Morgan also acknowledged the importance of the series being played at such a difficult time amid the pandemic, describing the role it could play in providing some relief and entertainment as "huge".

"As a sportsman, there are very few times you play sport or contribute to things when people actually really need it," he said. "I went through this experience myself towards the back end of our first lockdown period when sport just started to be reintegrated into people's TVs at home, and the smile it put on my face and the community that I live in was outstanding.

"Given the circumstances, how bad they still are, particularly at home, it's important for us to go out there and hopefully put on a bit of a show. Because it's certainly a lot of different challenges at this moment in time but certainly sport can help relieve that a little bit."