Two meters or less?

The Director of Public Health of Quebec, the Dr Horacio Arruda, announced Monday morning a relaxation of the rules of physical distance in certain contexts and for young people under 16 years old. As of June 22, theaters and cinemas will be able to accommodate 50 people, 1.5 meters away, and young people under the age of 16 will be able to get closer to one meter. However, some countries have already adopted such distancing rules for their entire population.

While the World Health Organization recommends maintaining a distance of at least one meter between people to prevent the transmission of COVID-19, France stands by this recommendation by requiring its population to respect a meter distance between citizens. In Belgium, Germany and Australia, we opted instead for 1.5 meters. In the United States, it has been determined that six feet, or 1.8 meters, is required. In Canada, like the UK and Switzerland, two meters are required. But why then impose two meters if other countries manage to deconfinate with a distance of one meter, knowing that for many services, such as public transport, restaurants, theaters, museums, one meter less completely changes the game?

“This is a delicate question because it is at the heart of the risk assessment and the decisions that the government must take on the terms of the deconfinement. But if we want to be consistent, we will have to rely on scientific data. We must also take into consideration the probability that an infected person will be close to us, as well as the risks and benefits of the choice that will be made, “says Dr Marc Dionne, medical consultant at the National Institute of Public Health of Quebec (INSPQ).

The medical journal The Lancet recently published an article in which the authors have reviewed and analyzed the results of more than 200 studies that have assessed, among other things, the risk of transmission of the virus according to the physical distance between two individuals.

This article shows that, if you are less than a meter from another person, the risk of contracting or transmitting COVID-19 is 12.8%, while if you maintain a distance of one meter and more, this risk drops to 2.6%. If you step back two meters, the risk is further reduced by half and is only 1.3%. “Standing at a meter already reduces the risk of becoming sick by almost 80%. The benefit of going from a distance of less than one meter to that of one meter is much greater than that of going from a distance of one meter to two meters, “notes the Dr Gaston De Serres, epidemiologist at the INSPQ.

In addition, “as there are fewer cases [de personnes infectées] that at the start of the epidemic, the impact of standing two meters rather than one meter is necessarily less than when the disease was more common, “he said.

“Of course, two meters will better protect against transmission, but keeping two meters brings a lot of constraints. Decision makers must weigh the risks against the benefits. If only the risk of transmission is taken into account, two meters would be better than one meter. But if we consider the various situations of life in society, as in buses, the distance of two meters causes great difficulty in carrying out the transport of all users, “he continues.

Decision-makers must weigh the risks against the benefits

According to the Dr Dionne, “For our kids in daycare or school, the damage from keeping two meters away is probably greater than the risk that they run of being seriously ill if this rule is relaxed. For various other activities, the constraints imposed by two meters compared to one meter will explain and possibly justify choosing a meter, “he adds.

“Not only the distance, but also the source of transmission, ie the viral load of the infected person, and the duration of exposure are important in the risk of transmission”, underlines for his part the Dr Donald Vinh, infectious disease specialist at the McGill University Health Center. “Nurses and respiratory therapists who treated very sick people with very high viral loads contracted the disease after only ten minutes of exposure. However, rubbing shoulders with an asymptomatic person, whose viral load is much lower, in a grocery store for ten minutes does not entail the same risk. “

One meter poses an acceptable risk for the general population

The distance to maintain between people also depends on the context, continues Dr Vinh. “If we are in a park, outside, where there are good drafts, it would be acceptable to reduce to one meter, but not if we find ourselves with 25 people in a room, like a small restaurant . “

“One meter poses an acceptable risk for the general population, but for people at high risk of developing a severe form of COVID-19 or having complications, such as the elderly, it would be better to keep a distance of two meters in their presence, “he believes.

The right decision to make is therefore not so obvious. One thing is certain, “the first meter of distance must be maintained. We can then decide that, even if we are less well protected, the disadvantages of standing at two meters are so great that we will tolerate a slightly higher risk of COVID-19, “says Dr De Serres, before giving the example of the French authorities, who chose to adopt the distance of one meter. “This choice allows more transmission than that of two meters, but in the French context, asking for two meters was perhaps physically impossible, given the fact that they are more numerous and that the spaces are more limited. If we want our society to function, we have to tolerate a certain level of transmission. The French authorities therefore considered that this consequence was more tolerable than those caused by a distance of two meters which would not have allowed, or made possible, deconfinement, “he explains.

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