Rosberg has a cold and no news about future (GMM) Nico Rosberg appeared in the Interlagos paddock on Thursday with a slight cold.
"It's nothing serious," the Williams driver told Germany's Auto Motor und Sport.
German Rosberg, 24, said he had no news to tell amid speculation he is set to leave his team of four years in order to switch to Brawn with Mercedes backing.
"I can't even say when a decision is going to be made, because I don't know," he explained.
Insiders however believe the move is all but set in stone, and Rosberg has admitted that leaving Grove based Williams is an option at the end of his expiring contract.
He spoke glowingly of both Williams and Brawn in conversation with reporters at Interlagos.
"Williams has been my home," he said. "It's been a long time and it's been a very good time."
As for Brawn, he praised not only the Brackley squad's meteoric start to the season, but also its progress as its hugely funded rivals pushed to catch up.
"I think they have done well to keep the momentum going, although surely they've had a difficult time because they've had to cut staff and their budget has (reduced).
"That's not easy for a team and I think they've pulled through it really well," said Rosberg.