The average number of new daily cases across a week in the US was 175,809 on Wednesday -- the highest on record, and more than two and a half times greater than the previous peak in late July.

And Covid-19 deaths in the US are spiking.

More than 2,100 deaths were reported on Tuesday and Wednesday each, the first time that level was crossed on consecutive days since late April.

The average number of daily deaths across a week -- 1,658 on Wednesday -- is the highest it's been since mid-May.

The CDC recommended last week that Americans should not travel for Thanksgiving.

More than 1.07 million people passed through US airport security checkpoints on Wednesday alone -- the most in one day since March 16, around the time when coronavirus restrictions started nationwide, the Transportation Security Administration said Thursday.

More than 5.9 million people have flown through US airports since the CDC's anti-travel recommendation last week, according to TSA data.

During that same period, around 7 million confirmed cases of symptomatic Covid-19 were reported nationally, the researchers said.

As of Thursday, health authorities have identified more than 12.7 million Covid-19 cases total in the United States so far, according to Johns Hopkins University.

"We estimated that in the US through September 30, 2020, there were approximately 53 million total SARS-CoV-2 infections, including 42 million symptomatic illnesses and 2.4 million hospitalizations, with large variations by age group and geographic area," the CDC researchers wrote in the study published in the journal Clinical Infectious Diseases on Wednesday.

Fifty-three million would be about 16% of the US population of 330.6 million.

To estimate the number of Covid-19 cases that might have been missed since the beginning of the pandemic, the researchers used a model to adjust the reported numbers of symptomatic cases in the United States.