Is coronavirus transmitted by air and should everyone wear masks

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

Science popularizer Ed Yong answers the most controversial questions posed by the pandemic.

The coronavirus epidemic continues, and many are now panicking over things they never thought about before. Can I go outside? What if a person is walking towards, and the wind is blowing from his side? What if you need to wait out the red light, and someone is already at the intersection? What if on a run you see another runner approaching and the track is narrow? Everyday little things suddenly began to demand deliberate behavior.

This is largely due to the fact that data on the coronavirus is constantly changing. Until recently, it was officially believed that the virus is transmitted only through close contact with an infected person or objects. But some time ago, doubts arose. News began to emerge indicating that the coronavirus is likely to be airborne as well. Let's try to figure it out.

Is the coronavirus airborne

The confusion has arisen due to the fact that, in the scientific sense, "airborne" is not the same as simply "airborne."

If a person has contracted a virus that causes respiratory tract infections, they emit viral particles when they speak, breathe, cough, and sneeze. These particles are trapped in balls of mucus, saliva and water. The shell of large balls does not have time to evaporate, and they settle on the surrounding surfaces. They are traditionally called respiratory drops. For smaller balls, the shell evaporates faster than they fall. As a result, the "dried up" particles remain in the air and float away further. They are called airborne droplets of infectious particles, or aerosol.

When scientists say that a virus is "transmitted by airborne droplets," like measles and chickenpox, they imply that it travels as a suspension of infectious particles. And when the WHO said that the new type of coronavirus "is not transmitted by airborne droplets," she meant that it spreads primarily through respiratory droplets falling directly on a person's face or on surrounding objects.

However, according to Don Milton, who studies the spread of viruses in the air, the traditional separation into short-range droplets and long-range aerosols is based on outdated data. For example, scientists from the Massachusetts Institute of Technology have proven that exhalation, sneezing and coughing create rotating, rapidly moving clouds, consisting of both respiratory droplets and aerosols. And they spread much further than previously thought.

In a common sense, we can say that the coronavirus is airborne.

Therefore, now we should be concerned with other issues. How far do the particles travel? Are they stable and focused enough at the end of their journey to infect someone?

Several studies have provided preliminary answers to these questions. One team of scientists injected fluids containing the virus into a rotating cylinder to create a cloud of infectious particles. They found that inside this cloud, the virus remained stable for several hours. However, this does not mean that everything happens the same with the air on the street.

The researchers themselves noted that the conditions of the experiment are an artificial environment, and its result does not reflect what happens when you just walk down the street. “These conditions, rather, are close to invasive medical procedures such as intubation (insertion of a tube for mechanical ventilation of the lungs - Approx.ed.), which are at risk of aerolizing the virus,”explains Saskia Popescu, an epidemiologist at George Mason University in Virginia.

Other researchers from the University of Nebraska have found traces of coronavirus RNA (the genetic material of the virus) in the wards where the patients lived. Most had mild symptoms. Viral RNA was present not only on such obvious objects as a bed and a toilet, but also in hard-to-reach places: on ventilation grills, an outdoor window sill, on the floor under the bed. Moreover, RNA particles were found even outside the doorstep of the ward. However, this is not yet a reason for panic.

Finding viral RNA in a sick room is like finding a fingerprint at a crime scene.

As of April 13, the Nebraska team has failed to detect a live pathogenic virus in air samples. If found, this will mean that even people with mild symptoms can release coronavirus particles into the air, and he is able to move at least through the hospital ward. The latter assumption is supported by several other studies (first, second).

But even this does not guarantee that there is a threat everywhere in the air. Are these viral particles in sufficient concentration to infect someone else in the same room? How many particles do you need for this? How far does the virus travel outside and in other rooms? Has such movement influenced the development of the pandemic?

There are no answers to these questions yet. To get them, says epidemiologist Bill Hanage, you would have to expose animals to varying amounts of airborne viruses, see if they become infected, and compare this with the levels of the virus in places with infected people. “Such work will take years, no one will find the answer right now,” says the scientist.

Is it safe to go outside

All the experts I spoke with while writing this article agree that it is mostly safe. What's more, walking is essential to maintain mental health. Distance and ventilation are important to protect against infection; both are sufficient outdoors. The risk arises from the fact that many people gather close to each other, and not because the air is filled with some kind of viral fumes.

“People imagine clouds of viruses roaming the streets and chasing after them, but the risk of infection is higher when you are closer to the source,” explains Lincy Marr of Virginia Tech, who studies airborne infections. "Going outside is a great idea, unless you're in a crowded park."

In February, scientists from Wuhan took air samples from various public places, and it turned out that the virus was either completely absent or was present in incredibly low concentrations. There were only two exceptions: in front of the supermarket and next to the hospital. But even there, for every cubic meter of air, there were less than a dozen viral particles. It is not yet known how many SARS ‑ CoV ‑ 2 particles are needed for a person to become infected, but there are calculations for the first coronavirus (SARS) of 2003, and this number is many times greater than the number of particles found by researchers from Wuhan.

“I think we will find out that SARS ‑ CoV ‑ 2 is not particularly stable in the environment, like many other viruses,” says microbiologist Joshua Santarpia of the University of Nebraska. "You shouldn't get into large groups outside, but it's still a great idea to go for a walk or sit on the front veranda on a sunny day."

In order not to dwell on the possible risks when you go for a walk, Lincy Marr advises the following. Imagine that all passers-by are smoking, and choose your road so as to inhale as little smoke as possible. When someone passes by, and there is nowhere to move, you can hold your breath. “I do it myself,” says Marr. - I don't know if it helps, but in theory it can. It’s like walking through a cloud of cigarette smoke.”

There is no consensus on the rules of conduct in the premises. Take, for example, shops - one of the last mainstays of social life. Someone is more concerned not with the air inside, but with surfaces that are touched by many people, and after leaving, they must treat their hands with an antiseptic. Someone tries to go to supermarkets when there are fewer people. It is also recommended to stay as far away from other shoppers as possible and for store owners to improve ventilation.

Of course, there are other common areas, such as staircases and elevators. The latter are the most dangerous because ventilation is limited in them. Use common sense: if you hear neighbors coming out, wait a bit before going out yourself. If you have shared ventilation with them, don't panic or block the vents. Ventilate the apartment once or twice a day.

Should everyone wear masks

This is the most controversial issue. So far, everyone agrees only that this is a must for medical workers. There is no consensus about the rest. For months, WHO, the US Centers for Disease Control and Prevention, and most public health officials have said that you should only wear a mask if you are sick or caring for a sick person. They also admitted that there is an acute shortage of masks for medical personnel.

In April, the tension reached a critical point. Scientists and journalists began encouraging Western countries to use masks extensively, following the example of East Asia. Masks have become mandatory for all visitors to supermarkets in Austria and everyone leaving home in the Czech Republic and Slovakia. In the US, the Centers for Disease Control and Prevention has changed their guidelines to advise covering your face in public.

If the virus is airborne, it seems obvious that a mask will stop it. But the data of scientists are very contradictory, especially on surgical masks that do not fit tightly to the face.

Some studies have found that masks reduce the risk of influenza-like infections, slow down the transmission of influenza in the home, and even reduce the spread of the SARS virus, especially when combined with hand washing and wearing gloves. Other studies have been more controversial, finding that masks provide no benefit at all, provide little benefit, or help only when other measures are taken.

However, there is one good reason for using masks. Even if they cannot catch the virus from the environment, they will not let the virus coming from you out. According to the latest data, people infected with milder forms of coronaviruses emit fewer viral particles when wearing surgical masks.

“I was pretty dismissive of the masks, but I looked at them from the wrong side,” says Bill Hanage. "They are not worn so as not to get infected, but in order not to infect others." In the situation with SARS ‑ CoV ‑ 2, this is especially important because it is spread even by those who do not yet have symptoms.

Since people carry the infection before symptoms appear, then everyone should wear masks in public.

And yet they are not a panacea. China advocated wearing masks from the very beginning, but still could not contain the spread of the infection. In Singapore, masks were used primarily by medical workers, but the increase in infections has been reduced there. Countries supporting mask wearing relied on other measures as well, including extensive testing and self-isolation, and many were better prepared for the epidemic because they had already faced a similar situation in 2003.

In Asia, masks are not just protection, but a confirmation of citizenship and conscientiousness. They are also important as a symbol in other countries. When widely used, masks can serve as a signal that society is taking the epidemic seriously, reduce hostility towards the sick and calm down a little people who cannot afford to self-isolate at home and are forced to work in public places.

With all this, there are fears that masks can harm, especially for those who are not used to them. They create discomfort, people touch them, straighten them, move them to wipe their mouths, remove them incorrectly, forget to change.

In addition, due to the shortage of ready-made protective equipment, many sew them on their own. According to research, homemade sheet masks are less effective than medical masks, but still better than nothing. Marr advises using thick fabrics for them and sewing so that they fit properly to the face. Reusable masks should be washed thoroughly after use. And it's important to remember that they will not completely protect you.

The mask is a desperate measure for a situation where social distancing is not possible. Do not think that if you wear it, then you can freely communicate with everyone.

The debate about the benefits of masks is so intense, because much is unknown, and the stakes are high. “We're trying to build an airplane in flight,” Hanage says. "You have to make decisions with global consequences in the absence of reliable data."

The coronavirus epidemic is evolving so rapidly that years of social change and scientific debate have shrunk to months. Scholarly bickering affects public policy. Well-established rules are changing. The experiment, carried out in a hospital room, changed the attitude of people to the surrounding air in a couple of days. Yes, masks are a symbol, but not only of consciousness. They also symbolize a world that is changing so quickly that there is no time to take a breath.

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