Daniel Ricciardo tested positive for Covid-19
We know the reason why Daniel Ricciardo was unable to participate in the Bahrain winter tests. The Australian driver tested positive for Covid-19.

Lando Norris will thus have to handle the entire testing program for McLaren in Bahrain. His teammate Daniel Ricciardo, who tested positive for Covid-19, is required to observe a period of isolation in accordance with the local authorities in Bahrain, as stated in a press release from his team. The statement further adds that the driver will be fit in time for the season’s opening on March 20th.
This is the tenth positive result among Formula 1 drivers. In 2020, Sergio Perez, Lance Stroll, and Lewis Hamilton each had to miss one or more races due to the virus.
During the 2020-2021 off-season, Charles Leclerc, as well as Pierre Gasly and Lando Norris, also contracted Covid. Finally, in 2021, Kimi Räikkönen was forced to skip the Dutch and Italian Grand Prix, and Nikita Mazepin skipped the one in Abu Dhabi, before it was announced last December that Charles Leclerc had tested positive for a second time.