CHICAGO (CBS) — COVID-19 is already taking a toll on Major League Baseball, as the Miami Marlins’ games are postponed through Sunday after a nearly 20 positive coronavirus tests.

That alarming news has athletes rethinking their plans. A star of the Chicago Bears says he won’t play in 2020 over health concerns.

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And as CBS 2’s Jim Williams reported Tuesday, even with lots of precautions, it will not be easy for sports this year.

It’s been a hopeful a sign – a bright spot – in this year of the pandemic: baseball is back. But now, less than a week into the shortened season, 17 members of the Marlins’ traveling party have tested positive for COVID-19.

“Because of how infectious the virus is, just one case can turn into many cases, as we’ve seen recently with the Marlins,” said Dr. Benjamin Singer of Northwestern Memorial Hospital.

The Marlins’ crisis shows what an enormous challenge it will be for all of baseball to keep going, Singer said.

“You have so many moving parts, involving travel, a lot of people coming together at one time – not just players, but staff, trainers and everyone else involved with the enterprise of putting on truncated season,” Singer said.

It has shaken the sports world. Chicago Bears’ star defensive lineman Eddie Goldman is sitting out this season over health concerns, as are multiple members of the New England Patriots.

Football is an even bigger enterprise than baseball – many more players, coaches, and staff, and lots of contact. So how can it be played?

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“It’s going to be hard. The strict way – and this may be incompatible with putting together a football season – would be to have everyone in a bubble, to have everyone involved only around themselves, be tested before they kind of go into the bubble and then have strict rules,” Singer said, “and that may not be possible.”

If football isn’t played, the economic impact will be devastating – billions of dollars gone.

“Disaster in the making,” said entrepreneur and Northwestern University professor Paul Earle.

Earle said something else would be lost if the pandemic sidelines sports – a cultural glue in these fractious times.

“Sharing a passion for a sports team cuts across all economic lines, ideological lines – we’re all together as one,” Earle said, “and, you know, metaphorically, I often use this phrase – we’re all wearing the same jersey.”

The NBA, WNBA, and professional soccer are all operating in bubbles. The National Hockey League resumes play this weekend in two cities only – Toronto and Edmonton.

Under the NFL’s current plans, players will be tested twice before entering team facilities and then tested every day. There will be no preseason games, and in-person meetings have been reduced.

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Though training camp is open, the Bears won’t be on the field until next month.