Nevada Gov. Steve Sisolak has ordered a three-week "statewide pause" that begins Tuesday to curb the spread of the novel coronavirus.

"I am not issuing a shutdown order," Sisolak said during a virtual press conference Sunday evening. "My goal is to aggressively try to attack this spread, while maintaining some portion of our economy and our daily lives."

Under the pause, residents will be required to wear face masks in private and public gatherings. Public gatherings will be limited to 50 people or to 25% capacity, whichever number is lower. Private gatherings will be limited to 10 people from no more than two households.

Sisolak said no additional businesses will be closed, but bars and restaurants will only be able to operate at 25% capacity with no more than four people per table. Gyms and fitness studios may operate with no more than 25% capacity while adhering to strict social distancing guidelines. Retail establishments including mall can continue operating at 50%.

"I know the majority of our bars and restaurants are doing their best, but these settings have proved to be high risk because they allow the opportunity for people to remove their face coverings in indoor settings around people outside of their households," Sisolak said. "That’s how the virus spreads."

ABC News' Marilyn Heck contributed to this report.

Russia confirmed 25,173 new cases of COVID-19 and an additional 361 fatalities from the disease in the last 24 hours, according to the country's coronavirus response headquarters.

It's the first time that Russia has reported over 25,000 newly diagnosed infections in a single day, setting a new record for the country. The cumulative total now stands at 2,114,502 confirmed cases, including 36,540 deaths, according to the coronavirus response headquarters.

Despite the growing number of infections and deaths, Russian authorities have repeatedly said they have no plans to impose another nationwide lockdown. Kremlin spokesman Dmitry Peskov told reporters Monday that it's up to regional authorities to decide what measures need to be imposed in their regions to curb the spread of the virus.

The Eastern European nation of 145 million people has the fifth-highest tally of COVID-19 cases in the world, behind only the United States, India, Brazil and France, according to a real-time count kept by Johns Hopkins University.

ABC News' Alina Lobzina contributed to this report.

There were 142,732 new cases of COVID-19 confirmed in the United States on Sunday, according to a real-time count kept by Johns Hopkins University.

It's the 20th straight day that the country has reported over 100,000 newly diagnosed infections. Sunday's count falls under the all-time high of 196,004 new cases on Nov. 20.

An additional 921 fatalities from COVID-19 were also registered nationwide on Sunday, down from a peak of 2,609 new deaths on April 15.

A total of 12,247,487 people in the United States have been diagnosed with COVID-19 since the pandemic began, and at least 256,783 of them have died, according to Johns Hopkins. The cases include people from all 50 U.S. states, Washington, D.C. and other U.S. territories as well as repatriated citizens.

Much of the country was under lockdown by the end of March as the first wave of pandemic hit. By May 20, all U.S. states had begun lifting stay-at-home orders and other restrictions put in place to curb the spread of the novel coronavirus. The day-to-day increase in the country's cases then hovered around 20,000 for a couple of weeks before shooting back up and crossing 100,000 for the first time on Nov. 4.

U.K.-based pharmaceutical giant AstraZeneca and England's University of Oxford announced Monday that late-stage trials show their COVID-19 vaccine was up to 90% effective in preventing the disease.

The results are based on interim analysis of phase 3 trials in the United Kingdom and Brazil, which looked at two different dosing regimens. One regimen showed vaccine efficacy of 90% when the drug, called AZD1222, was given as a half dose, followed by a full dose at least one month apart. A second regimen showed 62% efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens showed an average efficacy of 70%, according to press releases from AstraZeneca and Oxford.

There were a total of 131 COVID-19 cases in the analysis, and no hospitalizations or severe cases of the disease were reported in participants receiving the vaccine candidate, according to the press releases.

"These findings show that we have an effective vaccine that will save many lives," Andrew Pollard, director of the Oxford Vaccine Group and chief investigator of the Oxford vaccine trial, said in a statement Monday. "Excitingly, we’ve found that one of our dosing regimens may be around 90% effective and if this dosing regime is used, more people could be vaccinated with planned vaccine supply."

AstraZeneca, which has promised not to profit from the vaccine "for the duration of the pandemic," said it will now immediately prepare to submit the data to regulators around the world -- including in the United Kingdom, Europe and Brazil -- that have framework in place for conditional or early approval. The company will also seek an emergency use listing from the World Health Organization for an accelerated pathway to vaccine availability in low-income nations.

Meanwhile, Oxford said it is submitting the full analysis of the interim results for independent scientific peer review and publication.

"Today marks an important milestone in our fight against the pandemic," AstraZeneca CEO Pascal Soriot said in a statement Monday. "This vaccine’s efficacy and safety confirm that it will be highly effective against COVID-19 and will have an immediate impact on this public health emergency. Furthermore, the vaccine’s simple supply chain and our no-profit pledge and commitment to broad, equitable and timely access means it will be affordable and globally available, supplying hundreds of millions of doses on approval."

The U.K. government has already placed orders for 100 million doses of the AstraZeneca/Oxford vaccine candidate, along with 40 million doses of another developed by Pfizer and BioNTech which has shown to have 95% efficacy.

The actual number of people infected with the novel coronavirus in the United States reached nearly 53 million at the end of September, according to a model developed by scientists at the Centers for Disease Control and Prevention.

The scientists estimated the cumulative incidence of COVID-19 in the U.S. population by taking the laboratory-confirmed case counts that were reported nationally and adjusting them for sources of under-detection based on testing practices in inpatient and outpatient settings. Preliminary estimates using the model found that 2.4 million hospitalizations, 44.8 million symptomatic illnesses and 52.9 million total infections may have occurred through Sept. 30.

"This indicates that approximately 84% of the U.S. population has not yet been infected and thus most of the country remains at risk, despite already high rates of hospitalization," the scientists wrote in a report published in the Nov. 25 issue of the journal Clinical Infectious Diseases.

There were 6.9 million laboratory-confirmed cases of of domestically-acquired infections that were detected and reported nationally through Sept. 30. Since then, the CDC's tally has increased to nearly 12.5 million. Based on the model's ratio, the true estimated total would now be more than 95 million.