Racing Point driver Lance Stroll says he tested positive for coronavirus after the Eifel Grand Prix weekend.
The Canadian - who did not race - was unwell and displayed a number of Covid-19 symptoms at the Nurburgring race but was not tested over the weekend.
Stroll said his symptoms were "pretty mild" and he went home on the morning of the 11 October race and took a test.
He had another test on Monday, before this weekend's Portuguese Grand Prix, and returned a negative result.
"I feel in great shape and I can't wait to be back with the team and to race in Portugal," he added on social media.
Racing Point did not report Stroll's illness at the Eifel Grand Prix to governing body the FIA as a potential Covid case.
They said in a statement on Wednesday that this was because "a doctor did not believe his symptoms indicated Covid-19 and did not advise a test was necessary".
"Based on this clinical assessment, at the time there was no requirement to inform the FIA as to the nature of the illness," the statement added.
A spokesman for the FIA said it would not be taking any further action because "we don't feel that there has been any breach of the (Covid) code".
The FIA's code of protocols for dealing with Covid-19 says participants must "comply with the instructions of his/her Stakeholder (team) and the Covid-19 Delegate" if "he/she tests positive for the Covid-19 virus or he/she starts to suffer from any Covid-19 symptoms".
BBC Sport can reveal that Stroll's father Lawrence, who owns the team, has also contracted coronavirus.
Lawrence Stroll was tested at his Swiss home on the Sunday of the Eifel Grand Prix and returned a positive result, the team said, adding that he has been isolating since but has had no symptoms.
He had not travelled to the Russian Grand Prix or the Eifel GP.
Racing Point's statement said that Stroll first developed a stomach upset over the Russian Grand Prix weekend.
He tested negative for Covid-19 "several times" over the two weeks before the Nurburgring race, the team said, and again before travelling to Germany.
His stomach upset returned on Saturday morning at the Nurburgring, "which forced Lance to withdraw from the race and stay in his motorhome away from the paddock".
"Lance then flew home to Switzerland on a private plane on Sunday morning," the team added.
"In line with Racing Point's enhanced testing protocol, under which all team members are tested on return from a Grand Prix, Lance took a Covid-19 test at home and received a positive result the next day.
"He continued to isolate for 10 days from the date of the test, in line with local regulations. He returned a negative test on Monday this week and will travel to the Portuguese Grand Prix.
"All members of the Racing Point team at the Eifel Grand Prix returned to the UK via a private charter flight and all tested negative upon their arrival, and again in their pre-event test for the Portuguese Grand Prix."
Team principal Otmar Szafnauer said at the Eifel Grand Prix that he was "confident" Stroll did not have coronavirus, despite having "flu-like symptoms", an upset stomach and was "just not well in himself and couldn't exercise".
This was despite those being listed as possible coronavirus symptoms on the websites of both the World Health Organisation and the US's Centre for Disease Control.
Stroll is the second Racing Point driver to contract Covid-19 this year. His team-mate Sergio Perez was forced to miss the two races at Silverstone in the summer after catching the virus following a trip home to Mexico to see his mother.