New research has found that a larger number of COVID-19 patients than previously thought may not show symptoms, leading CDC to reconsider its recommendations against the general public wearing masks.
Current guidance—and concerns about promoting mask use
The spread of the new coronavirus has prompted dramatic increases in purchases of face masks, with some pharmacies reporting they're completely sold out. Other sellers are backordered for the products. Public health experts have urged the general public not to purchase masks and other personal protective equipment (PPE) that is needed more urgently by health professionals.
For instance, CDC currently recommends that the general public do not need to wear masks or cover their faces unless they are sick and coughing, or if they are in contact with people who are infected, according to the New York Times. Instead, the federal government recommends healthy people practice social distancing and remain six feet away from others in public.
Ilhem Messaoudi, an epidemiologist at the University of California at Irvine, said that since the new coronavirus is typically spread through fairly heavy respiratory droplets, social distancing and frequent hand-washing are the best ways to prevent infections.
"Given the shortage of PPE available to our health care workforce, it is irresponsible for anyone to suggest that we should all don masks, reducing the supply for nurses and physicians who do not have the luxury of treating symptomatic, very sick patients from six feet away," Messaoudi said.
Similarly, Surgeon General Jerome Adams said that "we still have PPE shortages across the country" and that masks should be reserved "for the people who most need it," such as health care providers. While "there may be a day when we change our recommendations—particularly for areas that have large spread going on—about wearing cotton masks," Adams said, "the data is not there yet."
There is also a concern that facemasks could provide people with a false sense of security, which could lead them to not practice social distancing as strictly, the Washington Post reports.
New research prompts questions
However, new data shows that there may be more people carrying the new coronavirus who are not showing symptoms than previously thought, according to CDC Director Robert Redfield.
Redfield said as many as 25% of people with the new coronavirus may not show symptoms. And although researchers are unsure exactly how many of those people are asymptomatic and how many are presymptomatic, Redfield noted that some infected people are transmitting the virus days before they show symptoms.
Specifically, a study published Wednesday in CDC's Morbidity and Mortality Weekly Report assessed 243 cases of COVID-19, the disease caused by the coronavirus, diagnosed in Singapore between January 23 and March 16. The researchers found seven "clusters" where the disease was likely transmitted before infected individuals showed symptoms, and in four of those clusters—where researchers could determine the date of exposure—such "pre-symptomatic" transmission happened between one and three days before the infected individual began presenting symptoms.
CDC noted that while the cases were carefully examined, it was feasible that an unknown source caused the clusters of infection, and/or that the study's findings could have been affected by potentially incorrect case reporting—especially if people who were sick experienced only mild symptoms.
Similarly, research from a team led by Benjamin Cowling, an epidemiologist at the University of Hong Kong, looked into data from the early days of the new coronavirus pandemic in China and found that China had left out most mild and asymptomatic cases. As a result, the team from the World Health Organization originally concluded that most people with the new coronavirus had significant symptoms, thereby underestimating the scale of the outbreak.
"We've estimated in China that between 20% and 40% of transmission events occurred before symptoms appeared," Cowling said.
Some health experts recommend masks
Amid these findings, some health experts have begun pushing the federal government to recommend the general public wear masks, including Scott Gottlieb, former FDA commissioner.
Gottlieb has recommended people wear improvised cotton masks, designed similarly to a bandana or a surgical mask. While such masks won't provide absolute protection from the virus, Gottlieb said, they could limit the respiratory droplets the person wearing the mask emits.
"The value of the mask isn't necessarily to protect you from getting sick, although it may offer some protection," Gottlieb said. "It's to protect you from other people. So when someone who's infected is wearing a mask, they're much less likely to transmit infection."
Gottlieb said studies on the flu have found that wearing a mask can reduce your ability to spread the virus by roughly 50%.
Separately, George Gao, the director general of the Chinese Center for Disease Control and Prevention, has said the "big mistake in the U.S. and Europe" is that "people aren't wearing masks." Gao said masks could "prevent droplets that carry the virus from escaping and infecting others."
Meanwhile, a review in The Lancet of advice on mask-wearing from several different countries ultimately concluded, "It would be reasonable to suggest vulnerable individuals avoid crowded areas and use surgical face masks rationally when exposed to high-risk areas. As evidence suggests COVID-19 could be transmitted before symptom onset, community transmission might be reduced if everyone, including people who have been infected but are asymptomatic and contagious, wear face masks."
What CDC is considering
As a result of this new data, CDC is considering changing its current recommendations. Redfield said research on masks was "being critically re-reviewed, to see if there's potential additional value for individuals that are infected or individuals that may be asymptomatically infected."
An official from CDC said the agency is also reviewing its recommendations because of a request from the White House coronavirus task force.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said there is a concern that a recommendation could lead to greater shortages of PPE, but added that "[t]he idea of getting a much more broad communitywide use of masks outside of the health care setting is under very active discussion at the task force. The CDC group is looking at that very carefully."
Meanwhile, Adams cautioned the public that "[e]ven if you do wear a mask, it can't be at the expense of social distancing," and noted that a mask like an N95 mask wouldn't be necessary because it could exacerbate shortages for health care workers.
Separately, President Trump during his daily news briefing, when asked whether he thought the general public should wear face masks given the shortage of supplies for health care workers, said while it wouldn't hurt for people to wear masks, scarfs could be a comparable alternative if procuring masks diverted them from health care providers.
"It doesn't have to be a mask. It can be a scarf," Trump said, adding, "What I do see people doing here is using scarves. And I think in a certain way, depending on the fabric, … a scarf is … actually better."
According to Politico, there is "no evidence" that scarves provide superior protection against the coronavirus than do face masks (Choi, Politico, 4/1; Mishra/Chander, Reuters, 4/1; Achenbach et. al., Washington Post, 3/30; Goodnough/Sheikh, New York Times, 3/31; Forgey, Politico, 3/31; Wu, USA Today, 4/1; Mandavilli, New York Times, 3/31).