Where and when is the risk of getting covid-19 highest?

A coronavirus infection is more likely indoors, which does not mean that caution can be left out outdoors. And there are different factors that influence the level of risk indoors. There are some rules for fighting covid-19 that most of you will have learned by now. The easy ones are washing your hands and keeping your distance from other people whenever possible. Then there is the “inner space: bad, open space: good” dichotomy when it comes to the risk of catching the coronavirus from those around us. But in reality it’s not that simple. Risk of Infection Depends on Many Factors One important route of transmission is the spread of coronavirus particles through aerosols and droplets, small airborne particles that an infected person emits when breathing, talking, or coughing. First, the most relevant. The risk of virus transmission is actually greater indoors. A 2020 Japanese study that examined 110 cases of covid-19 and its transmission pathways found that “the probability of a primary case transmitting covid-19 indoors was 18.7 times higher compared to an outdoor environment. “. But there are different factors that can affect how the virus spreads indoors. The Max Planck Institute of Chemistry has a calculator that allows you to set various parameters to determine the level of risk of contracting covid-19 if a person is infected. Factors influencing this include the volume of the infected person’s voice speaking, how much they participate in the conversation, and how well ventilated the room is. The calculations are based on a study of aerosol transmission and risk of infection published in the International Journal of Environmental Research and Public Health. Singing is risky One of the scenarios with the highest infection rate is a coral rehearsing. That’s because the louder an infected person vocalizes, the greater the concentration of droplets they produce, according to the study on which the Max Planck Institute bases its calculator. Loud singing also expels droplets farther away than just breathing or talking at a lower volume. As the study authors say, “singing is a particularly intense aerosol source.” Classrooms Avoiding this risk shouldn’t be too difficult. But what about a classroom? Many countries want to avoid a new cycle of school closures, but to make this possible and still keep the risk of infection low, there are several factors to consider. With an infected individual indoors, people are more likely to get sick in a classroom full of children than in an office full of adults. The reason: the number of fully vaccinated people is lower among children. Other risk factors include poor ventilation – in the Northern Hemisphere, opening windows every hour long enough to ensure fresh air circulation may not be an option with outside temperatures dropping to uncomfortable levels. And many schools don’t have air filtration systems. Effective masks Whether in the classroom, office or any other indoor environment, there is one measure that significantly reduces the risk of catching the coronavirus: wearing masks. A PFF2 mask (equivalent to other international standards known as N95, KN95 and P2 masks) can reduce the risk of infection by 20-fold, and the more advanced PFF3 masks can reduce the risk by 100-fold for the wearer, Ulrich told DW Pöschl, director of the Department of Multiphase Chemistry at the Max Planck Institute for Chemistry in the German city of Mainz. “Indoors, I would recommend masks whenever people mix with [outras] “I think masks should be worn by everyone.” That doesn’t make the other measures unnecessary, of course. Keeping your distance, trying to ensure a high level of ventilation and not singing remain important for keep the risk of infection low, even when everyone is wearing masks. Outdoor environments are not risk-free After all, how high is the risk of infection outdoors? Lower than when you’re indoors, of course. this doesn’t mean that you should leave all caution aside. “Also outdoors it’s useful to wear masks when you’re around other people,” said Pöschl. “From 1 to 2 meters [de distância], you are also at risk of getting infected by droplets. These larger droplets that we all exhale can reach other people outdoors as well. And just one of these droplets, about a millimeter in size, can cause an infection with a very high probability if it comes from an infected person.” Wearing masks, therefore, doesn’t just decrease the risk of catching the coronavirus indoors. As Pöschl said: “It’s just even more important to wear a mask indoors.” Author: Carla Bleiker

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