Niki Lauda's doctor has confirmed reports that the F1 legend will not be in Australia next month.

Lauda, who has just turned 70, has had a long recovery from lung transplant surgery last year.

"Niki is doing well at the moment," Lauda's younger brother Florian Lauda told ORF television.

"Now he has to strengthen his muscles, but the worry is over."

However, Lauda's doctor Walter Klepetko warned that "large crowds" could actually pose a risk to the triple world champion's health.

"Large crowds are always a potential threat of infection, in which case it may be appropriate for him to wear a mask to protect himself," he said.

But Dr Klepetko said Lauda will surely return to the F1 paddock soon enough.

"However, he will not be there for every race and most of all not in Melbourne at the start of the season," he said.

"A transcontinental flight is not what is needed now."

Responding to a birthday message from the broadcaster ORF, Lauda said: "It has been a bit bumpy, but I'll come back at full speed."

When asked about Lauda's birthday, world champion Lewis Hamilton said he talked to the Mercedes team chairman via FaceTime.

"We miss him, his advice is precious," said Hamilton.

"He has been through a difficult time, but he wants to get back to what he was doing before."