(CNN) — The 2020 Summer Olympics are finally underway in Tokyo.

Competition began Wednesday, more than a year after the original start date. The Games were delayed due to the pandemic, but with Covid-19 still spreading unchecked in Japan, organizers have been forced to take unprecedented steps to keep competitors and the public safe.

Athletes who contracted coronavirus have seen their Olympic dreams dashed.

Some tested positive in Japan, some before coming.

These are the athletes we know who have publicly dropped out due to Covid-19 health and safety protocols.

Team USA: 5

Katie Lou Samuelson — USA Women’s 3×3 Basketball

Coco Gauff — USA Women’s Tennis

Kara Eaker — USA Women’s Gymnastics

Taylor Crabb — USA Men’s Beach Volleyball

Bradley Beal — USA Men’s Basketball (Placed in health and safety protocol but hasn’t publicly disclosed a positive Covid-19 test)

Team Czech Republic: 6

Pavel Sirucek – Czech Republic Men’s Table Tennis

Ondrej Perusic — Czech Republic Men’s Beach Volleyball

Michal Schlegel — Czech Republic Cycling

Markéta Sluková-Nausch — Czech Republic Women’s Beach Volleyball

Barbora Hermannova — Czech Republic Women’s Beach Volleyball (Ruled out because her partner Sluková-Nausch tested positive for Covid.)

Pavel Širuček — Czech Republic Table Tennis

Team Great Britain: 3

Amber Hill — Great Britain Shooting

Dan Evans — Great Britain Tennis

Johanna Konta — Great Britain Tennis

Team Mexico: 2

Hector Velazquez — Mexico Baseball

Sammy Solis — Mexico Baseball

Team South Africa: 2

Thabiso Monyane — South Africa Men’s Football

Kamohelo Mahlatsi — South Africa Men’s Football

Team Australia: 1

Alex de Minaur — Australia Men’s Tennis

Team Chile: 1

Fernanda Aguirre — Chile Women’s Taekwondo

Team Netherlands: 1

Candy Jacobs — Netherlands Women’s Skateboarding

Team Russia: 1

Ilya Borodin — Russia Swim Team

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