This is great, as yelling right in somebody's face is just about the only way you're going to spread COVID-19 while you're actually playing baseball and outside on the field. It's pretty straightforward. Talking puts droplets in the air. Yelling puts lots of droplets in the air*. Even outside, if you're yelling in somebody's face, you will probably need less than the five minutes it typically takes face to face talkers to transfer enough of the virus to infect somebody else.
* Yelling over the sound of loud machines was one of the key contributors to the large outbreaks in meat processing plants in the Midwest. Combined with close contact and virus friendly cold air.
I actually think baseball is a perfect example of how we could do a lot better in general if we just dumb it down so everybody has simple rules to follow. Sit them all down and make it easy. Say this:
Guys, PAY ATTENTION! The CDC says this:
So here are your two rules you need to follow all the time, no exceptions:
1. If you're outside and can't maintain a steady 6 foot distance between you and somebody else, put on your mask. And pull it up all the way over your nose dummy. This disease is very happy to set up shop in your nose and drop virus right down into your lungs, which will make you very sick.
2. Inside, like in clubhouses, buses, training rooms, all those closed, poorly ventilated places where you guys spend lots of time together: WEAR A MASK. Period.
3. You should consider the dugout to be part of rule #2.
That's it. Even if somebody brings it into the team from home, it's very unlikely to spread to others if they just follow the basic guidelines.
IMO, there is no way the Marlins players followed any part of my rule #2. They totally spread it to each other in the training rooms. Probably working out in the gym together with no masks. Probably sat next to each other getting dressed for practices in the clubhouse talking face to face. Probably ate meals together face to face. To get that many people infected means that they were in all in close contact in small spaces for long periods of time.
Gee, how did we all get infected?