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After more than six months of the pandemic, it is already known that the use of masks, good hygiene and social distance are the most effective forms of prevention against covid-19. But what is the best way to make this distance? In which scenario is the contamination rate higher or lower? Based on asymptomatic cases, researchers at the University of Oxford and MIT developed a table that measures the risk of contagion by considering factors such as air circulation, size of the cluster and time of exposure to the virus.
Is it necessary to always be 2 meters away from other people outside the house? Is it possible to find friends safely? What would be the most appropriate location? These are questions that the study aims to help answer, although it has not yet determined a safe time in a place or the maximum number of people who can be together – talking, singing or even shouting – without compromising health. According to the article, published in the health journal The BMJ, the current rules of social distance – such as the 2 meters between two people – are simplified and date from studies made in the 19th century. According to the researchers, the delimitation of this distance does not take other important factors. “This ignores the dynamics of breathing, which emits moist droplets and forms a kind of cloud that carries them by the meter in a few seconds. After the deceleration of these clouds, ventilation, air flow patterns and the type of activity performed gain importance”, says the study. The viral load of the sender, the duration of exposure to the virus and the individual’s susceptibility to infection should also be considered.
The researchers hope that, by establishing degrees of contagion according to different situations, the recommendations for social distance can promote greater protection in high-risk scenarios and greater freedom when the characteristics indicate that the place is safer.
See the table, in the version of Portuguese website TVI:
The tables presented in the study have as variables the location (closed or open), the level of occupation (high or low), activity, contact time and the use or not of masks. Estimates refer to cases in which all individuals present are asymptomatic. The study considers that air particles are emitted by humans at speeds that vary according to the activity performed – such as speaking, shouting or singing. Coughing and sneezing can take these particles up to 7 or 8 meters away.
The environment also influences the spread of the virus. Air particles dissolve more quickly in open, well-ventilated areas. The study also makes reference to the coronavirus outbreak recorded in a choir in the United States, when 32 singers were infected despite maintaining social distance during the trials. The risk levels in the tables do not take into account susceptibility to infection. And it reinforces that social distance is not the only form of prevention and must be combined with hygiene, cleaning and protective equipment.
The information is from the newspaper The State of S. Paulo.