A declaration by a group of scientists calling for an approach that relies on "herd immunity" to defeat the coronavirus pandemic, which has been embraced by the White House, is "ridiculous" and "total nonsense," said Dr. Anthony Fauci, the nation's top expert on infectious diseases.

"That declaration has a couple things in it that I think are fooling people, because it says things that are like apple pie and motherhood," Fauci, director of the National Institute of Allergy and Infectious Diseases and a key member of the White House coronavirus task force, told ABC News chief anchor George Stephanopoulos in an interview Thursday on "Good Morning America."

The so-called Great Barrington Declaration, which claims on its website to have been signed by more than 9,000 medical and public health scientists around the globe, opposes lockdowns and argues that authorities should allow the novel coronavirus to spread among young, healthy individuals while protecting the elderly and the vulnerable.

"If you just let things rip and let the infection go -- no masks, crowd, it doesn't make any difference -- that quite frankly, George, is ridiculous because what that will do is that there will be so many people in the community that you can't shelter, that you can't protect, who are going to get sick and get serious consequences," Fauci said. "So this idea that we have the power to protect the vulnerable is total nonsense, because history has shown that that's not the case. And if you talk to anybody who has any experience in epidemiology and infectious diseases, they will tell you that that is risky and you'll wind up with many more infections of vulnerable people, which will lead to hospitalizations and deaths. So I think that we just got to look that square in the eye and say it's nonsense."

During a briefing Monday, World Health Organization director-general Tedros Adhanom Ghebreyesus called herd immunity "scientifically and ethically problematic.

"Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak, let alone a pandemic," Tedros said.

The U.K. government is expected to impose new restrictions in London as part of efforts to stop the rapid spread of the novel coronavirus.

Under England's new three-tier system of local COVID-19 alert levels, the British capital is expected to move up a level from "medium" -- the first tier -- to "high" -- the second tier -- at midnight on Friday. That means people from different households will no longer be allowed to meet indoors, including in homes, pubs and restaurants. Groups of no more than six people from different households can still meet outdoors.

Pubs and restaurants across London will continue to be allowed to stay open until 10 p.m.

London Mayor Sadiq Khan said the new measures are "deemed to be necessary in order to protect Londoners" but that he believes action is also needed "on a national scale," such as implementing a two-week lockdown. He said the city will soon reach an average of 100 COVID-19 cases per 100,000 population, a level some parts of England have already surpassed.

"I must warn Londoners that we've got a difficult winter ahead," Khan said in a televised statement Thursday. "But just as we've always done through our city's great history, I know that we’ll get through this dark time by pulling together."

The move comes as England saw its number of infections quadruple in the last three weeks. There are now more patients hospitalized with COVID-19 than when the country went into lockdown in late March, according to British Prime Minister Boris Johnson.

ABC News' Guy Davies contributed to this report.

Russia registered another 286 deaths from COVID-19 in the last 24 hours, setting a new record for its daily death tolls from the disease.

The country's previous record of 244 fatalities was set earlier this week.

An additional 13,754 new cases of COVID-19 were also confirmed in the past day, down from a peak of 14,231 registered the previous day. It's the first time in seven days that Russia didn't break its own record for single-day case counts.

The cumulative totals now stand at 1,354,163 confirmed cases and 23,491 deaths, according to Russia’s coronavirus response headquarters.

Russia, a country of 145 million people, has the fourth-highest tally of COVID-19 cases in the world, behind only the United States, India and Brazil.

ABC News' Alina Lobzina contributed to this report.

The national positivity rate for COVID-19 tests across the United States has jumped from 4.7% to 6% in week-to-week comparisons, according to an internal memo from the U.S. Department of Health and Human Services that was obtained by ABC News on Wednesday night.

The memo, which is circulated to the highest levels of the federal government and is used to determine daily priorities for the agencies working on COVID-19 response, said 38 U.S. states and territories are in an upward trajectory of new infections, while four jurisdictions are at a plateau and 14 others are in a downward trend.

There were 359,745 new cases confirmed during the period of Oct. 7-Oct. 13, a 17.1% increase from the previous week. There were also 4,962 fatalities from COVID-19 recorded during the same period, a 2.1% decrease compared with the week prior, according to the memo.

Meanwhile, 24% of hospitals nationwide have more than 80% of beds full in their intensive care units. That figure was 17-18% during the summertime peak, the memo said.

In Arizona, 6.71% of the state's prison population -- 2,599 inmates -- has tested positive for COVID-19, along with 712 prison staff. At least 17 inmates have died from the disease, according to the memo.

The number of new cases recorded in Washington, D.C., increased by 84% over the past week, after dropping to its lowest levels since July. The nation's capital reported an average of 81% of its inpatient beds occupied and 74.2% of intensive care unit beds occupied, the memo said.

Idaho's positivity rate for COVID-19 tests surged to 14.7% for the week ending Oct. 8, twice the national rate during the same period, according to the memo.

Indiana saw a 27.5% week-to-week rise in cases and a 23.4% week-to-week increase in deaths from COVID-19, as of Oct. 11. The state reported three consecutive days of record-high daily case counts from Oct. 8 to Oct. 10. The state's seven-day COVID-19 hospitalization rate reached a five-month peak at 17.3 per 100,000 population on Oct. 11, the memo said.

Minnesota's seven-day COVID-19 hospitalization rate also hit a five-month peak at 11.3 per 100,000 population on Oct.11. Minnesota reported a 19% increase in cases between the weeks ending Oct. 4 and Oct. 11, which state health officials said is linked to widespread transmission rather than clustered outbreaks, according to the memo.

Mississippi saw a 22.4% increase in COVID-19 cases in the week ending Oct. 11, compared to the previous week. The seven-day and 14-day averages for new cases continued to rise statewide, reaching levels not seen since early September. State officials are concerned that Mississippi is at the start of a second surge and have estimated that the cause of the increasing spread is sustained community transmission. Six major hospitals in the state were reported to have no more ICU surge capacity, the memo said.

Meanwhile, COVID-19 has devastated the Mississippi Band of Choctaw Indians, with the disease infecting more than 10% of the tribe and killing at least 81 of them, according to the memo.

North Carolina and Tennessee are two of five U.S. states that reported a greater than 50% increase in COVID-19 cases over the past week, the memo said.

COVID-19 hospitalizations continue to rise across Ohio, with the state's seven-day rate at 11.9 per 100,000 population on Oct. 11, according to the memo.

Pennsylvania recorded its highest daily case count in six months on Oct. 10 with 1,742 new cases. Multiple counties across the state reported a doubling of new cases during the period of Oct. 5-11, the memo said.

ABC News' Josh Margolin contributed to this report.