Dr. Anthony Fauci appeared on ABC News Live Wednesday and shared his thoughts on the U.S. Centers for Disease Control and Prevention's decision to lower its recommended isolation period to five days for asymptomatic patients.

Fauci also said that while new evidence shows  omicron may be less severe than delta, people should still be cautious of contracting and spreading the virus.

"You can get people safely back out in a five day period so long as they wear a mask, if they are without symptoms. That is the science," he told ABC News Live. "The impact of that is to try and not be in a situation where we essentially have to shut down the entire country."

Fauci also said it would be too premature to be less worried based on evidence that omicron may be less severe.

"We are heartened by the fact that from the South African data, the data from the U.K., and the accumulating data in the United States that it looks like it is less severe," he said. "It's much more transmissible, which is something you need to take seriously."

The U.S. Food and Drug Administration gave emergency use authorization to two over-the-counter COVID-19 tests.

The tests are manufactured by SD Biosensor and Siemens.

"Combined, it is estimated the companies can produce tens of millions of tests per month for use in the U.S.," the U.S. Department of Health and Human Services said in a statement.

-ABC News' Sony Salzman

The U.S. reported more than 1.9 million new cases this week, which equals about three Americans testing positive for COVID-19 every second.

The U.S. is now averaging 277,000 new cases each day, shattering the previous record average from Jan. 11, 2021, which was 250,000 cases each day, according to federal data.

Although this significantly high number is in large part due to the latest surge, it’s also attributable to the soaring demand for tests and backlogs of data following Christmas weekend.

-ABC News' Arielle Mitropoulos

In New York City, 30% of emergency medical workers and 17% of firefighters are out on leave tied to COVID-19 -- and the fire department is reminding New Yorkers to only call 911 in a true emergency.

"If you are not severely ill, allow first responders to assist those most in need," the FDNY said in a video message.

Meanwhile, the New York Police Department has canceled regular days off for Dec. 31 and Jan. 1 due to COVID-19 and staffing needs for New Year's Eve.

-ABC News' Mark Crudele, Aaron Katersky

Dr. Anthony Fauci strongly recommended against large New Year's Eve parties at Wednesday's White House briefing.

"Should you change or cancel your plans? If your plans are to go to a 40-50 person New Year's Eve party with all the bells and whistles and everybody hugging and kissing and wishing each other a happy new year, I would strongly recommend that this year, we do not do that," Fauci said.

Fauci said "all indications point to a lesser severity of omicron versus delta." But he warned, "we should not become complacent since our hospital system could still be stressed in certain areas."

White House COVID-19 coordinator Jeff Zients said, "We have directly helped more than 30 states and territories by deploying over 2,100 federal personnel and thousands of ambulances, ventilators and other critical supplies."

Supplies include gloves, masks, respirators and face shields, he said.

He added, "More than 13,000 National Guard members have been activated in 48 states to support the COVID response, from vaccinations, to testing, to clinical care."

At the briefing, CDC Director Rochelle Walensky defended the agency's shortened isolation guidelines.

"We do know the vast majority of viral transmission happens in those first five days, somewhere in the 85 to 90% range. So if a person can isolate for the first five days they absolutely should," she said. "We also don't know that antigen tests give a good indication of transmissibility at this stage of infection. On the other hand, we know that after five days people are much less likely to transmit the virus and that masking further reduces that risk. And this is why people need to mask for five days after the five days of isolation."

After five days, asymptomatic people with COVID-19 can leave isolation, but must wear masks around others, according to the new guidelines.

-ABC News' Cheyenne Haslett