WASHINGTON — Rep. Barbara Lee (D-Oakland) has tested positive for COVID-19, she said Tuesday in a statement.Lee, who is fully vaccinated and had also gotten a booster shot, said she received her positive test result this week.“Fortunately, I have only mild cold-like symptoms, but I know it could have been much worse had I not been vaccinated and boosted,” she said. “I am isolating and will follow all of the required health protocols to keep my loved ones, my staff, and my community safe.” Lee is at least the fifth member of Congress this week to announce having tested positive for COVID-19. On Sunday, Sen. Elizabeth Warren (D-Mass.), Sen. Cory Booker (D-N.J.) and Rep. Jason Crow (D-Colo.) disclosed their breakthrough cases, a term to describe people who test positive for the coronavirus despite being fully vaccinated. Each lawmaker said they had gotten a booster shot and that their symptoms were mild.Rep. Nicole Malliotakis (R-N.Y.) has also tested positive, according to local media reports.Earlier Tuesday, President Biden warned that the Omicron variant of the coronavirus could cause breakthrough infections “potentially in large numbers.” The Omicron variant has surpassed the Delta variant as the leading cause of infection. Federal officials reported Monday that nearly three-quarters of new cases last week were caused by Omicron.White House Press Secretary Jen Psaki said in a statement Monday that a “mid-level staff member” who had spent about 30 minutes near the president on Air Force One on Friday had tested positive for COVID-19. The staffer was fully vaccinated and boosted, Psaki said, and didn’t experience any symptoms until Sunday.Biden, who tested negative twice Sunday, will be tested again Wednesday.