On the street, in the store, in the office: how to protect yourself from the coronavirus while quarantining

How dangerous is a sneezing person at a bus stop for me? Do I need to go to a restaurant? How necessary is public transport? As the world gradually leaves quarantine and we return to the social environment, to our usual activities, the risk of infection and the spread of coronavirus increases. This causes fear of the second wave of the epidemic, writes Air force.

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The editors of the publication talked with the immunologist, associate professor of the University of Massachusetts in Dartmouth, Erin Bromage, about how to reduce the risk of catching COVID-19.

Dr. Bromage teaches a course on the epidemiology of infectious diseases and has been closely monitoring the development of the current pandemic from its inception.

He is not so much an expert on this particular disease as a skilled promoter of scientific knowledge. About 16 million people read his blog about the risks associated with coronavirus.

This is what he advises to do in the period of at least a partial return to normal life.

Where can I get an infection?

Dr. Bromage says that most people become infected in their own homes through another member of the family who passes the infection on to everyone else through constant contact.

What about outside the house? Are we putting ourselves at risk during our daily walk in the park? This frivolous runner without a mask - will he now transmit the disease to me?

Hardly, the professor believes.

“In the open air, the virus is sprayed in unlimited quantities,” he explained in an interview with the BBC. “Human exhalation dissipates very, very quickly.”

This means that your dose of the virus is likely to be insufficient to become infected.

“For you to get sick, a so-called infectious dose must enter your body - about a thousand particles of the SARS-CoV-2 virus. This assessment is based on studies of appropriate doses for MERS and SARS,” he wrote in his blog.

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The specific figure remains the subject of discussion and should be confirmed experimentally, but gives a useful overall picture of how a person becomes infected.

The main thing here is that you can get the required dose in different ways.

“A thousand viral particles in one breath, or a hundred in ten breaths, or ten in a hundred breaths. Any of these situations can lead to infection,” explains Dr. Bromage.

This means that in a very short contact with an infected person - the same runner who does not understand the need to maintain distance - you are unlikely to acquire an infectious dose.

In which situations should you worry more?

People with symptoms

Coughing and sneezing do spread infections, but in very different ways.

When coughing, a person throws about three thousand tiny drops into the air at a speed of 80 km / h at a time, says Dr. Bromage. Most of them are large enough to fall to the ground under their own weight, but some can remain in the air and fly to the opposite end of the room.

If the person with whom you are riding in the elevator does not cough, but sneezes, the risk increases by 10 times.

One sneeze is about 30 thousand particles moving at a speed of 320 kilometers per hour, and much smaller in size, so that they can easily reach even the farthest end of the room.

“If a person is infected, every time they cough or sneeze, they release as many as 200 million viral particles,” says Dr. Bromage.

“If you are talking to someone face to face and that person coughs or sneezes directly on you, then you, of course, can easily receive an infectious dose of a thousand viral particles,” the expert explains.

If you were not present during coughing and sneezing directly, you are still in danger. Some droplets can soar in the air for several minutes, and when you enter the room, you will have time to inhale enough of them.

Asymptomatic Distributors

We know that the first five days after infection, people get sick without symptoms, and in some they do not appear at all, even later.

Viral particles enter the atmosphere during normal breathing. But how many?

“With one exhalation, from 50 to 5000 droplets are released. Most of them move slowly and fall to the ground almost immediately,” explains Dr Bromage.

The number of drops is greatly reduced if a person breathes through his nose.

“The nose is an additional filter, and the air is directed vertically downward. Thus, the number of pathogens released - viral particles - is relatively small, the expert points out. “It is also important that during normal breathing, air comes out without effort, so that viral particles from the lower respiratory tract do not enter it.”

This is important because the concentration of coronavirus in the lungs and trachea of ​​an infected person is higher than in the throat and in the mouth.

How many particles of the SARS-CoV-2 virus (the current coronavirus causing COVID-19) are released during breathing is not known. But Professor Bromage cites research data, according to which, with ordinary flu, the patient distributes from three to 20 viral particles per minute.

If this data is also true for the pathogen COVID-19, then, being in the presence of an infected person, you should inhale absolutely all the particles secreted by him for 50 minutes in order to gain an infectious dose of a thousand particles (all data are estimated and approximate).

On the subject: Most patients with COVID in New York strictly enforced quarantine but became infected

Summing up, we can say that the probability of getting sick, just being in the same room with the carrier of the infection, is relatively small if he does not sneeze and does not cough.

However, most infections outside the home are likely to result from exposure to asymptomatic patients.

The risk increases by about 10 times if you talk, reminds Bromage.

Dramatically increasing the amount of droplets of saliva singing and screaming entering the atmosphere.

“As soon as you scream or sing, the droplets begin to literally bombard the space in front of you, and they come from the depths of the lungs, where the tissues are more infected,” says the specialist. “In general, any effort when exhaling sharply increases air contamination.”

What places are especially dangerous

Naturally, those who, due to their profession, deal with infected people are at greatest risk.

Also, cases of mass disease of people in certain places are known. In this regard, everyone remembers cruise ships. Dr. Bromage also refers to such environments as open office spaces, sports and leisure events, parties, funerals and choral rehearsals.

In all these cases, the risk of infection is great, because people spend considerable time indoors in the company of other people, among whom there may be carriers of infection.

“Even if a specific sick person is 15 meters away from you, as during a choir rehearsal or in a call center, and the number of virus particles reaching you is small, over a long period of time you can accumulate a dose,” the scientist assures.

As people return to their jobs, some professions are of particular concern.

The most common problems are open office spaces with poor ventilation. Dr. Bromage cites a case where in South Korea 216 employees worked in one large open space, and 94 of them fell ill.

There are not so many dentists in the general population, but they are a special risk group.

“During their operation, drilling, suction and other things, a large amount of aerosol substance is generated. Management should consider how to organize the work environment in a way that protects their employees, because the danger is primarily for dentists, not patients,” says Dr. Bromage.

Another risk group is teachers and lecturers.

“Teachers and instructors, mostly older people, must stay in the same room with young people for a long time. We need to think carefully about how to secure these workplaces,” the expert notes.

In the air and indoors

According to Bromidge, among the known episodes of mass infection, only very few happened outdoors.

Wind and space scatter the concentration of the virus, and sunlight, heat and humidity can shorten its survival.

By keeping your distance and shortening your contacts, you reduce the risk even further.

But some enclosed spaces are potentially very dangerous, especially events where people in crowded conditions talk to each other, sing and shout, and where it is difficult to effectively keep distance.

Rooms with poor ventilation and air conditioning are problematic.

Shops (at least for shoppers) are much less dangerous if you don’t stay in the same place for a long time.

Risk assessment

The restrictions associated with coronavirus are gradually being removed, but we must critically assess the degree of danger of certain occupations, Dr. Bromage advises.

If you are going to go into a closed space, take into account its cubic capacity, the number of people at the same time there and the duration of your stay in it.

"If you're sitting in a well-ventilated area with a small number of people, the risk is low," he says. — If you work in an open office, you need to evaluate its volume, number of people and ventilation. If your job involves face-to-face contact, much less loud talking and shouting, think carefully.”

On the subject: Quarantine exit: how to protect yourself from coronavirus if you return to work

For example, for a visitor to a shopping center, if he stays in it for a short time, and there are not very many guests and the volume of the room is large, then the danger is not so great. For a warehouse worker who spends all day there, it is significantly higher.

Outside, the risk of infection is much less, because the infected droplets dissipate quickly, but remember the dose and time, the professor notes.

“Until now, we have talked about airborne transmission of the virus, but we must not forget about surfaces. Infected droplets settle anywhere. Wash your hands frequently and avoid touching your face,” says Bromage.

And, probably, you will have to temporarily abandon the custom of blowing out candles on a birthday cake.

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