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

The newly updated CDC guidelines don't require testing at the end of isolation because PCR tests can stay positive for up to 12 weeks, CDC Director Dr. Rochelle Walensky told "Good Morning America" Wednesday.

"So we would have people in isolation for a very long time if we were relying on PCRs," Walensky said.

Walensky also addressed Tuesday's news from the FDA that, according to early data, rapid antigen tests may be less sensitive when it comes to the omicron variant.

"We do know that the most sensitive test you can do is a PCR test," Walensky said. "So if you have symptoms and you have a negative antigen test, we do ask you to go and get a PCR to make sure those symptoms are not attributable to COVID."

Walensky said rapid tests do work "quite well," especially in places where people are being tested regularly, like at schools.

"They may not work as well as they have for the delta variant," Walensky said, but "we still are encouraging their use."