Does the new virus mask have a protective effect? Absent?

Does the new virus mask have a protective effect? Absent? Feb 7 20:50

The outbreak of the new coronavirus has caused a "mask shortage phenomenon" such as masks sold out in various parts of Japan. Many people wearing masks are expected to have a protective effect. However, there is a great deal of information about the protective effects of masks against the new coronavirus. Can a mask be preventive? Or does it have no preventive effect? Here's what we know at the moment.

If you are coughing

First, there is one thing you can be sure about masks. It means that anyone with any symptoms should wear a mask.

Coughs and sneezes are said to lead to saliva and other flying flies about one to two meters. In the unlikely event that the virus is infected, this fly will be a major factor in spreading the virus.

This is a common feature of many viral infections, such as influenza and common coronaviruses.

For this reason, wearing masks correctly for people who have coughing or sneezing symptoms is, as it were, a "basic principle" to prevent others from transmitting or spreading the infection. This is the so-called "seki etiquette".

Cracking explanation

So what information is provided about mask wear for people who have no symptoms such as coughs?

From the homepages of major institutions in Japan and overseas, I checked the contents written about "masks for people without symptoms". The contents of the website are as of February 7. It may be updated in the future.

(1) Prime Minister's Office HP
"Using a mask for prevention is a precautionary measure, especially in places with poor ventilation, such as indoors and vehicles."

However, at the same time, he explained with an annotation that "the effect is not very noticeable unless it is quite crowded".

(2) Ministry of Health, Labor and Welfare HP
We set up a Q & A about the new coronavirus, but at least we could not find any statement about "Patients without symptoms should mask for prevention".

(3) Consumer Affairs Agency HP
He reminded him that repurchase purchases were not desirable and that they should be considered so that people in need of the mask could be secured. He urged him to check for precautionary measures on the Prime Minister's Office homepage.

(4) WHO (World Health Organization) website
In the Q & A, there is an item, "Should I wear a mask for prevention?"

Among them, there is no guarantee that infection can be prevented with a mask alone, and only people with symptoms are encouraged to wear a mask, so as not to waste valuable resources and use it incorrectly.

Also, in the "advice for mask use" linked in the same place, there is no scientific basis that a mask can be prevented, so it is stated that a mask is not necessary if there are no symptoms.

However, when nursing patients with the new coronavirus, they say that they should wear a mask.

(5) HP of CDC (American Center for Disease Control)
Guidelines for preparing for an influenza pandemic are described as valid for the outbreak of the new coronavirus.

It states that it is not recommended that people without symptoms wear masks to avoid infection unless there are special circumstances.

On the other hand, masks can be used when crowds cannot be avoided, when pregnant women and the elderly are at high risk of developing the disease, or when they come into contact with family members or other such people.

The conclusion of looking at the homepage examined this time is that although masks alone cannot be expected to have much preventive effect, they may help to some extent in certain environments such as crowds. However, scientific evidence suggests Does not exist ".

I don't know why

Why is there no scientific evidence?

If you want to scientifically determine whether a mask can prevent coronaviruses and influenza viruses, it is actually a very difficult experiment.

Divide as many people as possible into two groups, and make sure to check how much you are infected with the group that always wears a mask and the group that does not wear a mask at all.

A week or so may be too few to get infected and may need to be continued throughout the winter.

In the first place, many people in Asia, including Japan, use masks habitually, but the number of influenza patients and the epidemic situation in winter are less than those in Europe and the United States, where healthy people rarely use masks. there is no.

In fact, when the pandemic flu outbreak occurred at the time between 2009 and 2010, vaccination had begun, and preventive measures were widely discussed.

I think many people were wearing masks. Nevertheless, it became a huge trend.

Focus on sure things

Since there is no help for it, we will look at what is likely.

(1) The new coronavirus is thought to be infected by directly inhaling the virus-containing flying spots, or the virus scattered by the flying spots attaching to the hands and touching mucous membranes such as the face with the hands. (This is considered the same as a normal coronavirus)

(2) The virus does not float in the air and become infected by air except in a very limited special environment such as an ICU. (This is also said in the flu)

(3) Surgical masks (usually disposable masks) cannot shut out the virus itself, but do not pass through because flying particles are large.

(4) The virus is attached to the hand, and infection occurs if the hand touches the eyes, nose, mouth, etc.

(5) Even if you are wearing a mask, there is no preventive effect if you use it incorrectly, such as when your nose is out or just on your chin.

(6) It is sometimes explained that a virus attached to a hand is difficult to enter a nose or a mouth because a face cannot be easily touched when a mask is used. (However, when I looked around, I often saw a scene where I was touching my face with the mask shifted.)

(7) There is an opinion that it is safe to wear a mask.

I think there are other factors that need to be considered, but this is the summary of interviews with doctors and researchers.

Considering 1 to 5 together, it seems that even if there is some preventive effect, it is not so large, but rather it is more meaningful to wash out the virus on the hands and disinfect with alcohol.

"In normal life, masks for people with no symptoms are ineffective," said one infectious disease expert.

However, I feel that the security of 7 cannot be ignored.

"Think better than never"

"If you have no symptoms, you should think about it better than not." This is the word of one of the experts I interviewed.

If you do not have a mask at hand, you may want to focus on measures such as washing your hands and sleeping well so that you do not have to worry too much.

However, those who should reduce the risk of infection, that is, pregnant women who have a chronic illness, are older, are more susceptible to the virus, or who are at high risk for infection, should use a mask. It is better to put it on.

Currently, masks are reported to be out of stock, but masks that are not properly attached have no meaning in preventing infection.

I felt that we needed to think together about how to deliver the mask to high-risk people who need it.