United States House Speaker Nancy Pelosi has attacked Deborah Birx of the White House Coronavirus Task Force, linking her to “disinformation” spread by President Donald Trump.
Dr Birx replied that she always bases her decisions on science.
She is a prominent member of the task force, working alongside infectious disease chief Anthony Fauci.
Mr. Trump has regularly been criticized for his claims about Covid-19, many of which have been proven to be false.
What did Pelosi say?
Ms Pelosi commented on ABC’s This Week program, responding to a question about a report on the Politico website that she criticized Dr Birx in a meeting with other administration officials .
“I think the president has been spreading misinformation about the virus and she is her appointment, so I don’t trust her there, no,” Pelosi told ABC.
According to Politico, the House speaker used stronger words during his meeting last week with Treasury Secretary Steven Mnuchin and White House Chief of Staff Mark Meadows.
“Deborah Birx is the worst. Wow, what horrible hands you are, ”she allegedly told them. She also described Dr. Fauci as a “hero”.
Dr Birx told CNN’s State of the Union that she respects Ms Pelosi and believes the criticism was sparked by a New York Times article suggesting she was too ready to adopt overly optimistic assessments on the pandemic.
“It was not a Pollyan vision. I’ve never been called pollyannish, or unscientific, or non-data-driven, ”she said. “I will build my 40-year career on these fundamentals of using data to deliver better programs and save lives.”
In the same interview, Dr Birx said the United States has entered a “new phase” in its fight against the pandemic, with the disease being “extraordinarily widespread”.
She warned people living in rural areas that they were not immune and that they should take precautions such as wearing masks and social distancing.
She also urged Americans returning from vacation to assume they were infected and self-isolate – and she said people living in multigenerational households should consider wearing a mask at home.
Why are Trump’s comments being watched?
Dr Fauci clashed with Mr Trump over the use of the drug hydroxychloroquine, which the president has promoted as being effective in fighting the virus.
There is no evidence of this, and regulators warn the drug can cause heart problems.
Mr Trump also discussed irradiating the bodies of coronavirus patients with ultraviolet light, a concept that Dr Birx says cannot be applied as a treatment.
The United States continues to have the highest number of coronavirus cases in the world – more than 4.6 million – and more than 150,000 people have died there with the virus, more than in any other country.