The Center for Disease Control (CDC) and many organizations around the world have been telling people that they do not need to wear a mask if they are not sick or are not taking care of someone who is sick with the coronavirus.1 On the other hand, those in Wuhan are mandated to wear a mask: if such an individual ventures outside without one and is caught by the police, he or she is brought to a local police station. How can the Chinese attitude to the use of masks be so different from the United States one for the coronavirus?
In this report, we shall use science, reasoning and published information to address the potential usefulness of masks.
Person to Person Transmission
To understand the possible utility of masks, one needs to know how covid-19 passes from one individual to another. There are two main media: through “air” and by “land”. When a person infected with covid-19 sneezes or coughs, droplets are sent into the air. To a lesser extent, even when a person breathes out, very fine liquid particles also exit. These droplets can contain the coronavirus, and if they enter the body of another person, that person could become infected too.
(I) Infection Via Surfaces and Physical Transfer
In the case of a sneeze or cough, the relatively large droplets are sent flying out several feet before falling to the ground or a surface. The finer droplets remain suspended for some time (aerosols) but eventual they too can land on a surface. If an individual touches the surface and then touches his or her nose, mouth or eyes, then the virus has the possibility of infecting that individual. The coronavirus is stable up to four hours for smooth non-porous surfaces and up to one to three days for porous materials depending on the type of surface material.2 (II) Infection Through the Air
There are two possibilities in this case: (A) droplet projectiles and (B) airborne aerosols.
(A) Droplet Projectiles
If an infected person coughs or sneeze in the direction of a healthy person, then the droplets may hit the facial region of the latter allowing virus entry through the nose and/or eyes and possibly the mouth.
If a healthy person breathes in aerosols containing the virus, then the virus might enter the body through the person's mouth, nose and lungs. To a much lesser extent, entry through the eyes is also possible. The coronavirus is stable in aerosols for up to three hours.2 So, for example, a healthy person could enter an elevator in which an inflected person coughed an hour earlier and still get the coronavirus through these means.
“It would be a tragedy for the West to discover that
current preventative recommendations and social distancing
without mask use did not turn out to be effective enough
to control the covid-19 pandemic.”
Transmission of the coronavirus involves passing it from the infected one to the healthy one. Facial devices can work by capturing droplets and aerosols that an infected person exhales, or in the case of transmission by method II (through “air”) by protecting the healthy person from receiving infected material in the eyes, nose, mouth or lungs. To prevent viral matter from entering the eyes, goggles are needed, but in this report we do not discuss eyewear.
(i) The Simple Mask
Examples of the simple masks are bandannas, ordinary dust masks and surgical masks. These masks are capable of filtering out the bigger droplets but not the smallest ones. If a person has the coronavirus then wearing such a mask helps to prevent transmission by methods I and IIA because the droplets get caught in the mask. This is why health agencies recommend that people infected with the coronavirus wear masks. If a healthy individual wears a simple mask then it is preventive in the case of a type IIA event.
(ii) The N95 Respirator
This mask is designed to prevent at 95% effectiveness even droplets as tiny as 0.3 microns (aerosols generated by human coughing, sneezing and breathing) from passing through it. If a person with the coronavirus correctly wears an N95 respirator, there is a great reduction in all the above transmission methods. If a healthy person wears an N95 respirator, then it is effective against transmission through air (method II).
It is very important that a user of an N95 respirator make sure that it is airtight. If there is a small gap at some place where the mask meets the face and 50% of the air breathed in passes through this gap, then the effectiveness of an N95 respirator against transmission by method IIB is reduced in half.
Given the nature of how covid-19 is transmitted and the above understanding of how masks work, there has to be a benefit to wearing masks. However, it is difficult to quantify how much this benefit is. A Jupiter Scientific staff member went to the CDC website (on 3/22/20) to find out why the organization recommended the healthy public not to wear masks. There were three reasons: (a) it can be detrimental in that it gives people a false sense of security,
(b) the mask could cause people to touch it or their face more often, and (c) the masks are needed for health care providers and the current stockpile in the United States is not sufficient if the coronavirus outbreak worsens. All three of these arguments are valid. Nevertheless given that covid-19 is an airborne transmitted virus, the benefits of masks could outweigh the above three disadvantages. This is emphasized in a recent Lancet publication.3
Furthermore, it is possible to counter the above three negative reasons. Concerning (a), if use of masks in the most infected coronavirus regions were recommended, then in the information about the masks, people could be told that masks are just a supportive tool to primary prevention methods and people need to behave as if the masks were absent. In addition, because US citizens are not used to wearing masks, seeing everyone wear one could actually make the public more concerned and cautious.
As for (b), proper instructions need to be given with mask use. Currently, the CDC is telling people to wash their hands frequently and especially after touching public surface (such as doorknobs, handrails, shopping carts, coins, etc.) – so the mask should be viewed similarly: One should wash one's hands after mask use just in case viral matter has ended up on it. Concerning (c), the public should not buy the types of masks and respirators needed by health care professionals and by infected people; the the public could even be banned from doing so.
The use of dust masks, bandannas, possibly home-made masks, and previously used N95 masks and respirators (that might, for example, have been bought for the California wildfires or for other reasons) would not affect the medical supply shortage argument.
In addition, the public should be advised to make the masks as airtight as possible for two reasons: first, it adds a little more effectiveness to the prevention of droplet generation and, second, it might provide a little additional protection for the larger-sized components of aerosols in the case of transmission via method IIB.4 For flexible mask materials, air tightness can be verified by the collapse of the material to the mouth when breathing in through the mouth.
It may be possible to improve the air tightness of simple masks with tape around the boundary region.
Of importance in the argument for the public use of masks is that the incubation period (the time during which a person has the coronavirus but is not manifesting symptoms) has a mean of about 4 days but can be as long as roughly 2 weeks.5 During this period, the asymptomatic individual can transmit covid-19 to others. If there is a directive that those with the coronavirus stay inside and wear masks but asymptomatic people go to grocery stores and other public places while not wearing masks, then they are unknowingly violating the directive.
If everyone were to wear a mask, the public could be assured that asymptomatic infected people were also following the directive. In this context, the following statistic is striking: “Individuals with undetected infections were so prevalent in China that they apparently were the infection source for 86 percent of confirmed cases.”6
Current CDC Protocols
The CDC is currently recommending that people1
(1) Wash hands often with soap and water for 20 seconds especially after having been in a public place.
(2) Avoid touching their eyes, nose and mouth with unwashed hands. (Better is: (2) Do not touch the eyes, nose and mouth with unwashed hands; if one feels the need, then use a tissue or clean cloth).
(3) Keep a distance of six feet from others.
(4) Cover the mouth and nose when coughing and sneezing.
Many other recommendations apply to those taking care of sick ones and those who are sick.1
In many coronavirus-affected regions of the United States, people are currently required to stay at home and only go out for essential items – food and medications being examples. If people in such regions were required to wear masks, recommendations (3) and (4) would be better implemented because if two strangers accidentally get closer than six feet (while in a store or in a line, for example) and one coughs or sneezes, the matter would go into a mask. Recommendation (2) might also be better implemented (as long as one also washed one's hands after mask use) because one cannot touch one's mouth or nose while wearing a mask.
The following shows a graph of the active covid-19 cases in China as a function of time (in days) until the present (3/24/2020):
China has been successful in almost defeating covid-19 on the time scale of a couple of months. China did two things differently from the United States and Europe: (i) severe travel restriction leading to geographical containment and (ii) mask use. The former allowed the Chinese to largely contain the coronavirus in the Hubei Province, while in Europe the virus has spread from country to country and in the US from state to state.
Other countries that employ widespread mask use are Korea, Japan and Taiwan and all three have been considerably more successful than western countries in combatting the coronavirus. It would be a tragedy for the West to discover that current preventative recommendations and social distancing without mask use did not turn out to be effective enough to control the covid-19 pandemic.