Blues target Bersant Celina is facing three months out of football with the heart problem which Dijon manager David Linarès revealed at the weekend.
The 24-year-old contracted Covid late in June but returned to his club in mid-July, however, as a result of the virus subsequently developed pericarditis.
Kosovo-based journalist Arlind Sadiku said in a tweet that Celina is required to rest and expresses fears for his career.
"Bersant Celina has an infection (pericarditis) and needs to rest for three months,” Sadiku wrote.
"He is receiving treatment at home, and will return to the club in a month.
"We hope that this infection doesn’t turn into a chronic disease, because it could end his career.”
The NHS website says the condition often follows a virus: "Pericarditis causes chest pain and a high temperature. It's not usually serious, but it can cause serious health problems.”
As previously reported, Town have been in talks with the former loanee about a return to Portman Road for much of the summer.
Town were facing opposition from a number of other clubs for the forward's signature, reportedly including Championship Hull City and Coventry City, and clubs in the Dutch top flight where Celina previously played on loan with FC Twente in 2016/17, but remained interested until the heart problem emerged.
Celina spent 2017/18 on loan with the Blues from Manchester City, making 26 starts and 12 sub appearances, scoring eight times, in a successful spell under Mick McCarthy’s management.