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Stay at least one meter away. Wash your hands. Wear a bandage on public transportation.
You’ve probably heard the crown rules (maybe a little too) many times, but do you know when you need to be more careful to follow them?
A new review from the research journal British Medical Journal gives you a graphic overview.
– We have learned to keep our distance, but now some may start to get bored. So it’s good to have some general rules of thumb for when it’s most important to be careful, says Torben Sigsgaard, a professor in the Department of Public Health at Aarhus University.
He has not co-authored the new study, but thinks it is a good idea to give a more nuanced picture of when it is most important to be careful.
A good rule of thumb
– The model is quite crude and should be read with caution, because there are many factors that are not included. But it does give some good rules of thumb, says Sigsgaard.
Professor Lars Østergaard agrees.
– We do not have strong evidence in the area, so it must be read with reservations. But it makes sense to convey which situations are worse, says Østergaard, who himself researches the coronavirus at the Department of Clinical Medicine at Aarhus University.
– There is no doubt that it is important to avoid being many people together in a small and closed room. And if people sing and scream without a mask at the same time, it’s even worse, he adds.
Here’s what researchers have done
You can see the British Medical Journal form below.
The form is based on a review of the available research literature.
Although some fields on the form are green, this does not mean that the situation is free of risk of infection, the researchers emphasize.
– Green does not mean that there is zero risk, but that the risk is lower, explains Lydia Bourouiba, who is one of the main authors of the study and a professor at the Massachusetts Institute of Technology (MIT).
Among other things, researchers have included research on how droplets from coughs and sneezes can spread through the air.
What situations are riskier? A green field does not mean that there is zero risk of contagion, but that the situation is less risky than red and orange ones. (Graphics: Videnskab.dk, translated by forskning.no)
Speak, shout, sing
The form also takes into account if you are surrounded by people who are quiet, talking, yelling and singing.
– When we make loud noises, the spread of viruses increases, explains Torben Sigsgaard, who has done research in the field.
The fact that singing can be riskier became especially clear when the story of a cross singing exercise in Skagit County in the United States went around the world.
A study describing the episode claims that one of the choir singers was affected by COVID-19 and had symptoms of the disease during choir rehearsal on March 17, 2020. Although the choir participants kept their distance and consumed alcohol in hands, almost all 61 participants were infected: 33 cases of covid-19 were confirmed – and 2 died – while 20 people were “presumed” infected.
Research on other diseases also indicates that it can increase the spread of viruses when we speak, perhaps especially if you speak out loud.
Call factories
The new British Medical Journal study also indicates that special environments create an additional risk of infection.
There have been several crown outbreaks in slaughterhouses and meat packing plants. “The outbreaks have been attributed to a combination of high levels of infection by workers, poor ventilation, tight working conditions, background noise (leading to shouting) and little use of masks.”
In Denmark, a slaughterhouse in Ringsted was also recently forced to shut down temporarily due to a corona infection.
The researchers emphasize that it is difficult to know which situations and environments are more risky and point out that we must comply with the recommendations of the authorities.
Time and density of people
As you can see from the form, the model also takes into account whether you use a mask. To learn more about the use of masks, read the article What type of mask works best? Investigators filmed coughing and sneezing.
Another important factor, according to the new study, is the density of people.
A crowded area can be a concert, a nightclub, or a canteen.
The researchers emphasize that it is difficult to set clear boundaries.
Short or long?
We have also tried to get Professor Lydia Bourouiba to explain what “short” and “long” mean. She responds in an email that investigators still don’t know exactly where the line is going.
– But if you wear an effective protective mask, it is rare that viruses are transmitted in minutes, he writes.
He adds that the researchers do not include specific figures for time and density because they do not want to give people “a false sense of security.”
Torben Sigsgaard cannot offer fixed rules either.
– It is not possible to set fixed limits for the density of people and time. This is because it has to take all parameters into account, so it would be wrong to set exact numbers, it says.
However, as an example, point to the people you sit with in the office all day. That, of course, will take a long time to come.
Interior or exterior?
A final major factor for risk is whether you are outdoors or indoors. Several researchers have emphasized that it is safer to meet other people outdoors.
If you stay indoors, ventilation is important, notes Torben Sigsgaard.
– There should be ventilation with open windows and drafts, or controlled ventilation where air is drawn from the room and removed. Some ventilation systems reuse the air in the room, but avoid it, says Sigsgaard, who is part of a task force developing guidelines on ventilation and risk of infection.
– A normal fan on the desk does not count. In fact, it can make the situation worse by helping to mix the air in the room, she adds.
Read more about creating good ventilation in the box below the article.
Other important factors
Although the new model takes into account several different factors and situations, the researchers emphasize that the most important thing is to use common sense. There are several important factors that the model does not take into account:
- How susceptible you are to infections
- How much virus an infected person secretes
- Air currents in indoor premises
- Where you are in relation to the infected person
– Moisture can also be important, but is not yet unequivocally determined, the researchers write.
Good advice: how to get good ventilation in a room
Professor Torben Sigsgaard investigates, among other things, ventilation and the spread of infections.
Here he gives good advice on how to effectively ventilate your classroom, kindergarten, common office at work or other crowded rooms.
Create penetration
A single open window is not enough, the fresh air must expel the old one. Create ventilation by letting air in from one side of the room and out the other.
Ventilate once an hour
As a general rule, you should ventilate once an hour when there are many people in the room. If you do five to ten minutes of aeration, you will get fresh air for the next hour.
Penetration doesn’t make you sick
Many people are afraid of penetration because they have heard that it leads to disease. But drafts and drafts are not the same: draw a constant while the drafts are short-lived, and therefore you can stay in the room while it is ventilated.
Also air when it’s cold
It is important to continue ventilating even in autumn and winter with rain and cold.
Check if the ventilation system works
Ventilation is not necessary if the room has a mechanical ventilation system. But remember to check if the system works and if the filter needs to be replaced. The type of ventilation is also important. Some plants, typically older plants, circulate the same air. Therefore, virus particles can potentially run between facilities. If system recirculation cannot be turned off, you must shut down the system and use ventilation instead.
Source: Torben Sigsgaard
The case was first published on Forskning.no
Reference:
Nicholas R Jones mfl: Two meters or one: what is the evidence of physical distancing in covid 19? British medical journal, 2020. https://doi.org/10.1136/bmj.m3223
