Professional athletes could be particularly vulnerable to falling seriously ill with the new coronavirus, the head of a global union representing them told Reuters.
Brendan Schwab, the executive director of the World Players' Association, added some players were being asked to sign away rights that would normally give them legal and financial protection should they fall ill.
"We have seen some research that athletes may be particularly vulnerable to serious symptoms," said Schwab, whose union represents around 85,000 athletes, including many who play in the NBA, MLB, NHL, NFL, rugby, European soccer and Australian Rules football.
"The virus may get deep into the lungs, it is a virus that can cause severe damage not only to the lungs but other organs and athletes need to be at a very high level of health and fitness in order to be able to preserve their careers."
Schwab said while players were willing to take a calculated risk to resume their sporting careers, since social distancing rules cannot be adhered to in most sports, it would not be at any cost.
"We are concerned that some sports bodies are trying to place the economic and legal risk of contracting the disease on to players and that is something which we think should not be tolerated," he said.
Schwab said if players signed away their rights, they could be denied "the basic economic and legal protection which should go along with being injured or otherwise ill in the ordinary course of work."
He added, by taking part in contact sports, the "players themselves are being asked to do something which is inherently risky and inherently contrary to all of the health information that is being given."
"Player health and safety should be not be something which is negotiable because of the economic pressure sport is under at the moment," he said.
Schwab said the widespread testing was a key to ensuring elite sport could take place but athletes did not want it to be carried out at the expense of the general public.
"The players are making it very clear that they don't want to have a high level of testing if that is going to place the public health effort in jeopardy," he said.
Sports competitions which restart early, such as Germany's Bundesliga, had a special responsibility.
"We believe that those sports who want to try and go first, they do try and set the very best practices," he said.
"We were very impressed by the comments of Bayern Munich and Germany goalkeeper Manuel Neuer who was saying that, yes this is a leadership example, we as players have to step up to the mark. And, when it comes to health and safety, the leagues and the governing bodies need to do the same."