For How Long Is C-diff Contagious? My 22 Month Old

For how long is C-diff contagious? My 22 month old great-grandson has it & is presently hospitalized for it. This makes his 2nd hospitalization in 10 days. He has been on Flagyl for a week, but is not doing any better. We do not know how he caught this & it has been very difficult to treat. I am very worried about him. Please share info about this nasty infection. Thank you
A very worried Nana