WHO says there is no need for healthy people to wear face masks, days after the CDC told all Americans to cover their faces

• On April 6, the World Health Organization released new guidance saying that healthy people don't need to wear face masks to prevent coronavirus spread.
• Masks should be for the sick, their caretakers, and healthcare workers, the WHO guidance said.
• Scientists and public health organizations can't agree on the best face-mask protocol, and the WHO guidelines go against CDC face-mask guidelines.
• Visit Business Insider's homepage for more stories.

The use of face masks on healthy people during the coronavirus pandemic has been a major point of contention and confusion among scientists and the public.

On Friday, the US Centers for Disease Control and Prevention released new advice recommending that all Americans wear face masks when they are in public.

However, new guidance from the World Health Organization released on Monday asserts that healthy people don't need to wear face masks, and doing so won't provide added protection from the coronavirus.

There's some evidence that caretakers of infected people can protect their health by wearing masks, the WHO guidance noted, "however, there is currently no evidence that wearing a mask (whether medical or other types) by healthy persons in the wider community setting, including universal community masking, can prevent them from infection with respiratory viruses, including COVID-19."

WHO also said that community masking could lead to a "false sense of security" and cause people to ignore other evidence-based measures like hand-washing and self-isolation.

WHO says masks should be saved for healthcare workers, caretakers, and sick people - everyone else should just stay home

The WHO said that masks should be reserved for people who have COVID-19 or are in regular close contact with people who have COVID-19, like caretakers and hospital workers.

People with COVID-19 symptoms like a cough or shortness or breath should wear masks even if they haven't tested positive, and they should also self-isolate, seek medical advice from home, and practice good hygiene in hand-washing and taking off their mask, the WHO said.

They also said that healthcare workers should use medical-grade masks, not makeshift cloth masks, when they can after one study found that medical workers who used cloth masks were at increased risk of infection compared to those who used medical-grade masks.

"If production of cloth masks for use in health care settings is proposed locally in situations of shortage or stock out, a local authority should assess the proposed PPE according to specific minimum standards and technical specifications," the WHO report said.

Masks could slow transmission, but there's room for infection-causing human error

Some health experts believe community masking efforts can't hurt.

"The argument ... about everybody wearing a mask is not that it will prevent everyone from getting infected - it's that it will slow down transmission in the community a bit," Ben Cowling, a professor of epidemiology and a mask researcher at the University of Hong Kong's School of Public Health, previously told Business Insider. "That's already useful. Just to have even a small effect is useful."

At the same time, Cowlng recognized that face masks aren't a perfect public-health tool because they allow room for user error, a point made in the WHO guidance.

WHO officials said that healthy people who wear masks might touch their own faces more often than necessary, which could actually increase their risk for COVID-19.

Cowling said that user error is a potential reason studies have yet to show community masking is effective at preventing disease spread.

"Randomized trials don't support a big effect of face masks, but there is the mechanistic plausibility for face masks to work, right? So why not consider it?" Cowling said. "If you don't wear the mask properly, and if there's a lot of chances for you to get infected, then the mask may not do a lot of good."

But with much of the world already dealing with severe outbreaks, Cowling said masking efforts for the healthy are unlikely to stop the spread at this point in time.

"I think it's too late to do a lot for the current epidemic, because it's already spread such a lot, and then the cases that you're getting now are people infected two or three weeks ago. And the lockdowns that are in place will hopefully really slow down infections," Cowling said. "Adding masks now I don't think would make a lot of difference to that trajectory."

You can protect yourself without a mask

The coronavirus is typically spread through tiny droplets ejected from an infected person coughs, sneezes, or talks, and the droplets land on another person or surface.

Scientists are still studying to understand to what extent coronavirus-containing aerosols linger in the air, which would make face-mask wearing more important, Business Insider previously reported.

So far, evidence suggests that the virus does not seem to linger in the air outside of hospital settings, where certain procedures, such as intubating a patients, can aerosolize virus particles.

For people who isolate at home and practice social distancing when outdoors, aerosols are likely a non-issue. Running outdoors alone without wearing a mask, for example, is safe if you feel healthy, Business Insider previously reported.

As such, the WHO said, practicing self-isolation, good hygiene, and social distancing are the best ways for healthy people to stay safe. The organization said they'll also update their face-mask guidance based on new information as it comes out.