It is not yet clear when and how Mr. Trump contracted the virus. The president and the first lady said they had both tested positive hours after one of his closest aides, Hope Hicks,
also tested positive. Ms. Hicks received the diagnosis after she began experiencing symptoms on Wednesday while attending the president’s rally in Minnesota. Mr. Trump kept his appearance there to about 45 minutes, roughly half the length of one of his typical rally speeches.
Early Friday morning, it was still unclear how many other aides who had come into close contact with Mr. Trump had tested positive, but the White House said its medical unit was conducting contact tracing. Top advisers to the president described themselves as in a state of shock and said they expected a number of additional cases among people in Mr. Trump’s orbit. White House officials had hoped to keep the news about Ms. Hicks from becoming public, to no avail.