A new CDC report is warning that the virus "has entered a phase of high-level transmission" in the U.S. and that it's more important than ever to follow public health guidelines.

On Oct. 30, the number of new cases reported in the U.S. in a single day exceeded 100,000 for the first time, and by Dec. 2, the daily case number had nearly doubled, with over 196,000 new daily cases, the report said.

"With colder weather, more time spent indoors, the ongoing U.S. holiday season, and silent spread of disease, with approximately 50% of transmission from asymptomatic persons, the United States has entered a phase of high-level transmission where a multipronged approach to implementing all evidence-based public health strategies at both the individual and community levels is essential," the report said.

The report summarizes these strategies to combat COVID-19: universal face mask use, physical distancing, avoiding nonessential indoor space, increasing testing, prompt quarantine of exposed persons, safeguarding those at increased risk for severe illness or death, protecting essential workers, postponing travel, enhancing ventilation, hand hygiene and achieving widespread COVID-19 vaccination coverage.

-ABC News' Sony Salzman

COVID-19 will probably be ranked at least third for leading causes of death in the U.S. this year, Bob Anderson, Chief, Mortality Statistics Branch at National Center for Health Statistics, told ABC News.

"We won’t make that determination officially until all the data are in," Anderson added.

The No. 1 cause of death is heart disease, with 655,381 deaths, followed by cancer with 599,274 deaths, according to CDC data.

COVID-19 is in the No. 3 spot with 276,513 fatalities, followed by accidents which accounted for 167,127 deaths, according to the CDC.

-ABC News' Eric Strauss

Africa aims to have 60% of its 1.2 billion-strong population vaccinated against COVID-19 within the next two to three years, according to the head of the continent's public health agency.

"We hope that for that for this to be meaningful, our 60% must be reached in the next two to three years," John Nkengasong, director of the Africa Centers for Disease Control and Prevention, said at a press briefing Thursday. "We should be deliberate in this."

More than 2.2 million confirmed cases of COVID-19, including over 52,000 deaths, have been reported across the vast continent so far, representing a fraction of the world's cumulative count.

Moscow Mayor Sergey Sobyanin announced Friday the official start of a mass COVID-19 vaccination program in the Russian capital.

Residents are now able to sign up online to be vaccinated, and Sobyanin said some 5,000 people had registered in the first five hours since the launch.

"Teachers, doctors, social workers, those who today most of all risk their health and lives," the mayor wrote in a brief post on his blog Friday.

The announcement comes two days after Russian President Vladimir Putin unexpectedly ordered large-scale vaccination to start next week, despite earlier statements from the government saying the country has yet to produce enough vaccine doses to do so.

The mass inoculation campaigns will use Russia’s COVID-19 vaccine, called Sputnik V, which the health ministry controversially registered in August before starting crucial late-stage clinical trials. Vaccinations will be voluntary, with the drives first focusing on teachers and doctors.

Russia was still vaccinating volunteers as part of its phase 3 trial, which has so far only managed to inoculate 20,000 of a planned 40,000 people.

Putin has said that Russia will soon produce 2 million doses of Sputnik V, but it's unclear how many doses have been been produced so far and how many people will be able to be vaccinated from next week. The country has run into serious manufacturing hurdles and had to significantly cut its planned production from 30 million to 2 million by the end of the year.

ABC News' Patrick Reevell contributed to this report.