The US death toll from COVID-19 stands at more than 159,000, but nearly 300,000 Americans could die by Dec 1, University of Washington health experts forecast while saying that 70,000 lives could be saved if people adhered to wearing face coverings.

But the university's widely cited Institute for Health Metrics and Evaluation (IHME) said that the death toll could increase by more than 90,000 and bring it closer to 400,000 if the public doesn't comply with physical distancing and face coverings.

"We're seeing a rollercoaster in the United States. It appears that people are wearing masks and socially distancing more frequently as infections increase, then after a while as infections drop, people let their guard down," Dr Christopher Murray, director of the IHME, said in announcing the university's revised forecast on Thursday.

The US death toll is the most of any country in the world, with nearly 4.9 million known cases.

The IHME said infections were falling in the former epicenters of Arizona, California, Florida, and Texas, but rising in Colorado, Idaho, Kansas, Kentucky, Mississippi, Missouri, Ohio, Oklahoma, Oregon and Virginia.

Tennessee and North Carolina reported record single-day increases in deaths on Thursday with 42 and 73, respectively.

White House coronavirus task force coordinator, Dr Deborah Birx, identified new areas of concern during a telephone call with state and local officials on Wednesday.

Baltimore and Atlanta remain at a ``very high level," as well as Kansas City, Missouri, Portland, Oregon, Omaha, Nebraska, and California's Central Valley, Birx said on the call, a recording of which was obtained by the journalism nonprofit Center for Public Integrity.

Baltimore and Atlanta remain at a "very high level," as well as Kansas City, Portland, Omaha and California's Central Valley, Birx said on the call, a recording of which was obtained by the journalism nonprofit Center for Public Integrity.