Update April 4: After this blog was published, the CDC issued an advisory suggesting that everyone wear some type of face covering in public. The recommendation discourages people from using medical-grade or surgical-grade masks, such as N95 masks, and instead, leave those for medical professionals.
As we see the number of COVID-19 cases multiplying world-wide, the recommendations around whether or not we should all be wearing face masks are getting more and more confusing. Experts in China recommend that everyone should wear one. In other countries like Japan and Hong Kong, people are advised to wear them if they are going to be in a crowded area.
Here in the US, the CDC (Centers for Disease Control and Prevention) does not recommend face masks for people unless they are healthcare workers, sick, or taking care of someone that is sick. Similarly, the WHO (World Health Organization) directs that face masks don’t really prevent healthy people from getting infected from viruses.
So what should we be doing?
What experts agree on
When it comes to masks, there is strong agreement that N95 respirators (the kind of mask that requires fit testing) protect trained healthcare provider from getting infected through airborne and droplet particles in the healthcare setting. Surgical face masks help prevent the spread of infections through droplets among healthcare workers. There is also evidence that surgical masks help prevent sick people from infecting healthy people.
Experts also recognize that right now there are major shortages of protective face masks and respirators for frontline healthcare staff, so the general public should help by staying home and potentially donating their supplies to hospitals, until more masks become available.
How masks work
Basically, there are two major types of masks.
Surgical masks fit loosely in front of your mouth and nose. They are good at protecting others from droplets leaving the wearer’s mouth and offer some protection if someone sneezes or coughs around you. Again, because they are not airtight, airborne particles (particles that hang in the air) can still enter your mouth or nose when you breathe. From what we know so far, it is still not clear whether COVID-19 can be spread through airborne particles; WHO has put out information stating that this is not an airborne virus, but there is data that it can be aerosolized.
Respirators (people commonly hear of the N95 respirator) are meant to have a tight seal around the mouth and nose. They can prevent outgoing droplets, incoming droplets, and airborne particles, so are ideal for hospital workers that are in very close contact with sick people with certain conditions (especially when they are doing procedures).
The data on surgical masks effectiveness in preventing infections
Right now, we are basing what we know on data from the spread of other infections (like flu and SARS). It’s too early to have any definitive data from the COVID 19 pandemic.
There are a bunch of studies to show that face masks can be effective at preventing infection among healthcare staff in the hospital setting, even compared to N95 respirators. During the SARS epidemic one study found that 0% healthcare workers that wore a surgical face mask or respirator got infected (7% of those who wore a DIY paper mask did get infected).
When it comes to the general population in the “real” world, it’s much harder to say. Studies looking at face masks to prevent the spread of infection among family when one member was sick found that people were not consistent about using them, took them off after a few hours, and may not have done all the other things (like handwashing) to protect themselves. But in situations where people did follow instructions and wore the masks appropriately, there did seem to be benefit in reducing the spread of infection.
When it comes to N95 masks, they are only as effective as the seal. So, ideally, healthcare workers should be wearing them with a complete seal, especially if they are doing high risk procedures. If they are not worn correctly and are not tightly sealed, there seems to be very limited difference for healthcare workers (and by extension, the general population) between wearing a surgical mask and N95.
What to know if you want to make a DIY mask
After the H1N1flu pandemic of 2009, researchers at Cambridge University tested a whole range of household materials for DIY masks using particles both larger and smaller than the size of the new coronavirus.
They found that surgical masks worked really well- blocking 97% of large (bacteria-size particles) and around 80% of particles smaller than the coronavirus. But some materials for DIY masks also performed pretty well (for large particles: vacuum cleaner bags (95%), dish cloths (83%) and 100% cotton shirts (69%) and for small particles: 100% cotton shirts (50%)). They also tested for breathability, a key ingredient for successful use of a face mask, and found that 100% cotton t-shirts and pillowcases were the best.
Taken together, this information shows that wearing a face covering made from 100% cotton can be better than nothing. But remember, we don’t have any studies in the real life setting, so this is a "maybe"!
What about wearing a mask during the COVID-19 pandemic?
We know that the new coronavirus can be spread by people without symptoms and that symptoms can develop after 5 days (sometimes even longer). In this situation, it makes sense to wear a face mask if you have to go into a crowded area, especially for those who are at higher risk of complications (older people, those with a long-term medical condition, people with weakened immune systems and pregnant women).
Right now, since healthcare workers so desperately need masks to protect themselves, everyone that can should stay home so they don’t need to use them.
As the supply of masks grows, it seems reasonable for people to wear face masks if they need to be around others. The key is to remember that all of the other recommendations still stand: don’t touch your face, wash your hands, and dispose of the face covering safely without contaminating yourself.
While some do disagree about the role of face masks in protecting the general public from COVID-19, all experts agree that the main ways to protect ourselves is frequent, vigorous handwashing, disinfecting high-touch surfaces, keeping a distance of 6 feet from others, and staying away from sick people. Additionally, the main way that the general public can help during this pandemic is to maintain social distancing and stop going out for anything “non-essential.”