Birx warns of disturbing rise of coronavirus cases in 12 cities

White House coronavirus task force coordinator Deborah Birx said in a private meeting with local and state health officials that the task force is tracking increases in the virus in 12 U.S. cities.

"There are cities that are lagging behind and we have new increases in Miami, New Orleans, Las Vegas, San Jose, St. Louis, Indianapolis, Minneapolis, Cleveland, Nashville, Pittsburgh, Columbus and Baltimore, so we're tracking this very closely,” Birx said in the audio, first obtained by the nonprofit Center for Public Integrity. “We're working with the state officials to make sure we're responding together, but when you first see that increased test positivity, that is when to start the mitigation efforts.

"I know it may look small, and you may say that only went from 5 to 5.5 [percent], and we're going to wait and see what happens," she added. "If you wait another three to four, even five, days, you'll start to see a dramatic increase in cases. So finding and tracing those very early individuals is really critical."

Local officials in cities with rising rates of test positivity, Birx said in the Wednesday call, should practice aggressive mitigation.

However, two sources familiar with the call told CNN that at least two of the cities mentioned, Baltimore and New Orleans, were not represented during the call, and health officials there were unaware it was taking place, with Baltimore officials only learning their city was of particular concern when media outlets reached out for comment.