Amid the rapid spread of the new highly-transmissible Omicron variant, the US has reported more than one million Covid-19 cases in the last 24 hours, breaking previous records for single-day infection spike, according to health authorities.

As of 5 a.m. on Tuesday, the country registered 1.07 million confirmed cases in the past 24 hours, which increased the country's overall infection tally to 56,191,733, according to Johns Hopkins University.

The US remains the country worst hit by the pandemic, with the world's highest cases and deaths (827,749).

The number of new Covid-19 cases has doubled in the last seven days to an average of 418,000 a day, local media reported.

"The US reported more than 2 million coronavirus cases in one week, breaking yet another record as the Omicron variant surges across the country," reported USA Today.

However, the Centers for Disease Control and Prevention has decided to shorten the recommended times that people should isolate when they have tested positive for the virus from 10 days to five days if they don't have symptoms, a move that drew criticism from some medical experts and created confusion among the public.

"The rapid spread of the Omicron variant is weighing on U.S. businesses, keeping more workers home sick or quarantined and leading some companies to cut services and reduce hours," reported The Wall Street Journal on Monday.

The rise of daily cases to record levels in recent days has resulted in thousands of cancelled flights, prompted retailers to train available employees on new jobs or close some stores altogether, companies were quoted as saying.

"The rapidly spreading Omicron variant is hitting businesses at a time when consumers' demand for products and services has surged, and many companies already are struggling with staffing and supply-chain challenges," said The Journal report.