Check out this website to see some tips that Dr. Cross, pediatrician at Children's Hospital Los Angeles, suggests in order to best support your student during this time.
If it were up to the students, I'm sure they would hole up in their rooms all day, but this isn't productive and can lead to feeling isolated. Get them to go outside, even if it is just for a few minutes. Maybe go with them on a walk around the block or a quick morning run. Just try to go outside for at least 5 minutes everyday.
Knowing someone is in your corner can go a long way. Just letting them know that you are here for them and understand they might need a little extra help can make them feel a little less alone.