In a letter on Wednesday, Gianni addressed to Salahuddin as dear friend and said he had learned about the BFB chief diagnosed with Covid-19.
"From Zurich, I would like extend to you, on be half of the international football community and on my personal behalf, my best wishes for a speedy and complete recovery, with the hope to see you in full healthy very soon.
"Health is a top priority and I am accompanying you from distance to give you the strength to get through the period," the FIFA boss said.
A few days after testing positive for coronavirus, BFF President Salahuddin has been in self-isolation and remains in quarantine.
In a statement on Thursday, Salahuddin said he was feeling well, but still had some light symptoms.
“I've gone through so many messages, phone calls and letters over the last few days and I would like to genuinely thank everyone for their support, which is truly heart-warming. Thank you from the bottom of my heart," he added.