The spokeswoman for President Trump, Kayleigh McEnany, was also diagnosed with the coronavirus on Monday.
She says she will immediately be quarantined.
Her boss, Trump, was diagnosed with the virus on Thursday. His condition deteriorated rapidly, and he had to go to the hospital on Friday.
Many Trump associates and prominent party members have been infected.
They likely caught it earlier in the week at a well-attended Republican party rally where Trump spoke.