CDC encourages N95, KN95 masks to stop COVID-19 spread amid omicron surge

ATLANTA - The U.S. Centers for Disease Control and Prevention is now recommending people opt for the highly-protective N95 or KN95 masks over cloth masks to ward off the highly-contagious omicron variant and slow the coronavirus spread. 

"Masks are designed to contain your respiratory droplets and particles," the CDC said on its website. "They also provide you some protection from particles expelled by others."

RELATED: What type of face mask is best amid the recent omicron surge

Single-layer cloth masks may not provide adequate protection against the very infectious omicron variant of COVID-19, according to a recent Wall Street Journal report.

Many infectious disease experts noted people prefer cloth masks because they are more comfortable and fashionable to wear, but these masks can only block larger droplets of COVID-19, not smaller aerosols or particles that can also carry the virus.

Why is the CDC making the new recommendation now?

The CDC said that masks were previously in short supply but are considered better at filtering the air. In 

updated guidance posted late Friday afternoon, CDC officials removed concerns related to supply shortages and more clearly said that properly fitted N95 and KN95 masks offer the most protection.

Mask guidance has fluctuated over the course of the pandemic.

The CDC did not recommend healthy people wear face masks at first, but that guidance then changed over time. In April 2020, the CDC started advising people to wear cloth face coverings in public settings where social distancing was difficult to maintain. The CDC changed its guidance on face coverings as new information emerged about the spread of the novel coronavirus. Since the virus is highly contagious, even among people who may not be showing symptoms, the CDC recommended face masks as a way to prevent the virus’s spread.

RELATED: Omicron vs. delta: Study examines difference between two coronavirus variant symptoms

For much of the pandemic, the CDC advised Americans to wear masks indoors and outdoors if they were within 6 feet of one another.

Then in April 2021, as vaccination rates rose sharply, the agency eased its guidelines on the wearing of masks outdoors, saying that fully vaccinated Americans no longer needed to cover their faces unless they were in a big crowd of strangers. In May, the guidance was eased further, allowing fully vaccinated people to stop wearing masks outdoors in crowds and in most indoor settings.

But in July 2021, the CDC changed course on some masking guidelines, recommending that even vaccinated people return to wearing masks indoors in parts of the U.S. where the delta variant of the coronavirus was fueling infection surges.

The guidance still called for masks in crowded indoor settings, like buses, planes, hospitals, prisons and homeless shelters, but it cleared the way for reopening workplaces and other venues.

Some public health experts said they thought the earlier CDC decision was based on good science. But those experts were also critical, noting that there was no call for Americans to document their vaccination status, which created an honor system. Unvaccinated people who did not want to wear masks in the first place saw it as an opportunity to do what they wanted, they said.

What are the benefits and challenges of N95, KN95 masks?

According to the CDC, N95 masks filter 95% of airborne particles and have been approved by the National Institute for Occupational Safety and Health. 

RELATED: US omicron peak: Fauci predicts steep drop in cases toward 'end of January'

The masks also seal tightly to the face when fitted properly. However, N95 respirators cannot be washed. They need to be discarded when they are dirty, damaged or difficult to breathe through. The N95 respirators tend to be more expensive than masks.

KN95 masks are respirators that meet international standards. However, the CDC warns that about 60% of KN95 respirators in the U.S. are counterfeit and do not meet NIOSH requirements.

The CDC previously recommended N95 masks only for health care workers, advising people instead to wear cloth masks that have two (or more) layers of fabric that completely cover the face and mouth, fit ‘snugly’ against the sides of the face (without any gaps) that also has a nose wire to prevent air leaking from the top of the mask.

Who should wear a mask?

The CDC recommends people over 2 years old should wear a mask in indoor public places if they are not fully vaccinated. It’s also recommended for people who are fully vaccinated and in an area with substantial or high transmission — or fully vaccinated and with a weakened immune system.

The CDC said in general, you do not need to wear a mask in outdoor settings but should consider wearing one in crowded settings and for activities with close contact with others who are not fully vaccinated where COVID-19 cases are high. 

The current explosion of omicron-fueled coronavirus infections in the U.S. is causing a breakdown in basic functions and services — the latest illustration of how COVID-19 keeps upending life more than two years into the pandemic.

RELATED: Pfizer: Omicron-specific COVID-19 vaccine human trials to begin late January

Studies on the coronavirus and other germs show wearing a mask helps stop infected people from spreading disease to others. Evidence also suggests that masks may offer some protection for the people wearing them.

The virus spreads from droplets people spray when they cough, sneeze or talk. Surgical or cloth face masks can block most of those particles from spreading.

While some droplets may still spread out, wearing a mask could reduce the amount, providing a benefit to others. Research shows people don’t get as sick when exposed to smaller amounts of virus, said Dr. Monica Gandhi, a virus expert at University of California, San Francisco

How does the omicron variant differ from other variants?

The omicron variant spreads even more easily than other coronavirus strains and has already become dominant in many countries. It also more readily infects those who have been vaccinated or had previously been infected by prior versions of the virus. However, early studies show omicron is less likely to cause severe illness than the previous delta variant, and vaccination and a booster still offer strong protection from serious illness, hospitalization and death.

Scientists are seeing signals that COVID-19′s alarming omicron wave may have peaked in Britain and is about to do the same in the U.S., at which point cases may start dropping off dramatically.

The reason: The variant has proved so wildly contagious that it may already be running out of people to infect, just a month and a half after it was first detected in South Africa.

RELATED: CDC guidelines: When is the best time to get tested for COVID-19 after exposure? 

At the same time, experts warn that much is still uncertain about how the next phase of the pandemic might unfold. The plateauing or ebbing in the two countries is not happening everywhere at the same time or at the same pace. And weeks or months of misery still lie ahead for patients and overwhelmed hospitals even if the drop-off comes to pass.

The University of Washington’s own highly influential model projects that the number of daily reported cases in the U.S. will crest at 1.2 million by Jan. 19 and will then fall sharply "simply because everybody who could be infected will be infected," according to Mokdad.

COVID-19 cases continue to rise. According to the CDC, the 7-day moving average hovers around 750,000. That’s up from around 64,000 in late October. The 7-day moving average for COVID-19 deaths currently stands around 1,600, up from around 750 in late November.

FOX News and The Associated Press contributed to this report. This story was reported from Los Angeles.