Washington, D.C., Mayor Muriel Bowser's sister died Wednesday of complications from Covid-19, the mayor said.
Mercia Bowser, 64, was Bowser's older sister.
"Mercia was loved immensely and will be missed greatly, as she joins the legion of angels who have gone home too soon due to the pandemic," Bowser, a Democrat, said in a statement.
Mercia Bowser had been treated for Covid-19-related pneumonia.
"The baseline of daily infections is still very, very high," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said Sunday on NBC's "Meet the Press."
"It's not the 300 to 400,000 that we had some time ago, but we want to get that baseline really, really, really low before we start thinking that we're out of the woods," he said.
The number of U.S. deaths from the illness passed 500,000 on Sunday. And the next day, President Joe Biden addressed the nation and held a moment of silence for the dead. As of Wednesday evening, more than 28 million cases had been reported and more than 506,000 people had died, according to NBC News' count of reports.
Also Wednesday, documents released by the Food and Drug Administration indicated that Johnson & Johnson's coronavirus vaccine is, overall, safe and highly effective against the most severe outcomes of Covid-19.
In two days, an advisory panel is scheduled to discuss the company's application for emergency use authorization, which is expected to be recommended.