There’s a very powerful video going around from Rabbi Shimon Freundlich from Chabad Beijing that explains why outdoor minyanim are dangerous. It just takes a little wind to blow that droplet from the guy who sneezed or coughed on your clothing. You touch your clothing, then touch your face, and you’re infected. If you google Shimon Freundlich instagram, you’ll find the video.
Of course, the bottom-line reason you should daven at home is because all the rabbonim say so.