Niki Lauda has been released from Vienna General Hospital (AKH) after he returned to intensive care with a bout of flu. Lauda spent the second half of 2018 hospitalised after suffering a lung transplant
Doctors have previously revealed that the Austrian came mere days from dying, before he had both lungs replaced, prompting a long stay in intensive care.
After undergoing "intensive" rehabilitation in hospital and a separate clinic, Lauda was discharged in December and immediately headed for Ibiza with his family.
According to Heute, Lauda's wife Birgit had also fallen ill in Spain.
Lauda's immune system was weakened by his stay in hospital, while he remained too weak to visit grands prix in the latter half of last season, despite aiming to have returned at the Abu Dhabi GP.
Reports had suggested that Lauda had also come down with pneumonia while in hospital, although this was not confirmed by AKH.
The 2019 season-opening Australian GP remains a target for Mercedes' non-executive chairman to return to F1, although it is unclear if his latest trip to hospital will impact this.
Lauda delivered his own video update in November after Mercedes were crowned constructors' champions for a fifth year in succession, with Lewis Hamilton also winning a fifth drivers' title.