With the Tokyo Olympics scheduled for July, pressure is mounting on the International Olympic Committee to postpone the Games given the risks that athletes and visitors would face with the global coronavirus pandemic.

We’re already seeing some athletes struggle with the virus.

South African swimmer Cameron van der Burgh won gold at the 2012 Summer Olympics in London for the 100-meter breaststroke. He’s a world-class athlete and is 31 years old, but he has been struggling with COVID-19, the disease caused by the coronavirus.

In a Sunday Twitter thread, van der Burgh discussed his multi-week battle with the coronavirus, calling it “by far the worst virus” he had ever faced and urged the public to take preventive measures seriously.

2/ I have been struggling with Covid-19 for 14 days today. By far the worst virus I have ever endured despite being a healthy individual with strong lungs(no smoking/sport), living a healthy lifestyle and being young (least at risk demographic)

— Cameron van der Burgh (@Cameronvdburgh)March 22, 2020

4/ The loss in body conditioning has been immense and can only feel for the athletes that contract Covid-19 as they will suffer a great loss of current conditioning through the last training cycle. Infection closer to competition being the worst.

— Cameron van der Burgh (@Cameronvdburgh)March 22, 2020

6/ Please, look after yourself everyone! Health comes first - COVID-19 is no joke!

— Cameron van der Burgh (@Cameronvdburgh)March 22, 2020

According to van der Burgh, his symptoms have improved — and he no longer has a fever — but he raised issues that the IOC need to consider, especially when it comes to athletes preparing for the Olympics.

In a letter released on Sunday, the IOC set a deadline of four weeks to come to a decision on postponing the Tokyo Games. The IOC has, however, ruled out the possibility of canceling the Olympics.