Niki Lauda returned to the AKH hospital in Vienna last week after contracting a flu infection during the Christmas break.
Lauda, who turns 70 on February 22, was on a family holiday in Ibiza when he became ill.
It’s understood that the decision to take him to hospital was made purely as a precaution given his sensitivity to infection following his recent lung operation, and that there is no cause for alarm.
The Austrian, who turns 70 on February 22, underwent a lung transplant back in August, spending two months in the AKH hospital before he left in good condition.
In November he referenced his health in a video message issued to mark the fifth consecutive double world championship success for Mercedes.
“As you all know I had a rough time from my health point of view and the support I got from all you people on my way was unbelievable,” he said.
“And I was out of bed quicker because I felt to be home in a big strong family of friends.”