What experts know so far about the delta variant
The variant is rapidly outcompeting other versions of the coronavirus around the world
![a train conductor monitors people boarding a train car](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2021/07/070121_EG_delta_feat.jpg?fit=1030%2C580&ssl=1)
Passengers board a Missouri River Runner Amtrak train on June 11, 2021. The spread of the delta variant is causing concern, especially in places with low vaccination rates such as Missouri.
Charlie Riedel/AP Images