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Days after President Trump tested positive, White House press secretary Kayleigh McEnany has also tested positive for COVID-19.

USA TODAY

White House Press Secretary Kayleigh McEnany said she tested negative for COVID-19 “every day since Thursday” – until she tested positive Monday. 

McEnany’s disclosure shows the limits of daily testing in halting the spread of the coronavirus that causes COVID-19. A person might have such small traces of the virus after exposure a case isn’t identified until days later, even using the most accurate and sensitive tests.

It’s “what we call a window period: that’s the period after you get infected and before you test positive,” said Dr. Richard Scanlan, chair of the College of American Pathologists Council on Accreditation.

The widening outbreak of people connected to President Donald Trump brings new scrutiny to the White House’s strategy, which relies on testing everyone who comes in close contact with