TOKYO, July 21 (Reuters) - A member of the United States men"s beach volleyball team tested positive for COVID-19, NBC said on Wednesday, the first infection for an American who was expected to compete in the Tokyo 2020 Games. Taylor Crabb"s infection was detected over the weekend soon after he arrived in Japan, NBC said, citing his brother, Trevor, who told the broadcaster it was "terrible" and that Taylor was healthy and should be allowed to play. Two members of the U.S. women"s gymnastics team earlier tested positive, but they were alternates and not expected to compete, NBC said. A spokesman for the U.S. Olympic and Paralympic Committee did not immediately respond to a request for comment. The Tokyo 2020 Games, which are due to start on Friday, are being held under unprecedented conditions - including tight quarantine rules - to prevent the spread of COVID 19. Still, a number of cases have already emerged among athletes and other people involved with the Games.