White House spokeswoman Karine Jean-Pierre said she tested positive for COVID-19 on Sunday after returning from Europe with President Joe Biden, in the latest infiltration of the coronavirus into the West Wing's protective bubble around Biden.

Jean-Pierre, the principal deputy press secretary, said she last saw Biden “during a socially distanced meeting” on Saturday. Biden, because he is fully vaccinated, is not considered a “close contact" under Centers for Disease Control and Prevention guidelines.

Jean-Pierre traveled to Belgium and Poland with Biden after press secretary Jen Psaki tested positive for the virus last week.

Biden returned to the White House early Sunday morning from the four-day trip that saw him work to bolster the NATO alliance after Russia's invasion of Ukraine.

Jean-Pierre said she was experiencing “mild symptoms," adding that “in alignment with White House COVID-19 protocols, I will work from home and plan to return to work in person at the conclusion of a five-day isolation period and a negative test.”

The White House said Biden, 79, last tested negative for COVID-19 before returning to the U.S. from the trip as part of required pre-arrival testing.