Coronavirus: why do distancing measures differ from country to country?

Repeated tirelessly for months, the measure has become for many, a reflex. In the queues, the metro corridors or on the pedestrian crossings, everyone tries to leave at least a meter away from their neighbor. A move away recommended by all governments to stem the spread of Covid-19.

But if you look closer, these physical distances can vary from country to country. In France, it is "at least one meter", recommends the General Directorate of Health. Contacted on this subject, the latter specifies to copy his discourse on the "latest WHO recommendations". On its website, the World Health Organization thus stresses that "it is important to stay at least one meter from other people" in order to avoid the "inhalation of droplets" that can transmit the virus.

In other countries, one meter is not enough. Belgium, Germany, the Netherlands, Brazil and Australia recommend keeping at least "1.5 m distance" from each other. Finally, Spain, England, the United States ("6 feets") or Japan recommend a distance equivalent to two meters. Note, however: no country recommends its citizens to stay within one meter of their neighbor.

"Droplets that vary from one individual to another"

The lack of consensus around this distance is explained first of all by the lack of perspective from scientists on "the virus's capacity to spread", explains Fabienne El-Khoury, researcher at Inserm within the team of research in epidemiology. Above all, it seems complex to establish a precise and unique distance which would protect us from all risks. “We know that Covid-19 can be transmitted by droplets of saliva. But the size of these droplets can vary from one individual to another, ”says the epidemiologist.

In other words, a person can speak extremely quickly and turn around when another will, on the contrary, emit very few projections. Likewise, the risk of inhaling these postlets is not the same if you are in front of someone who sneezes or coughs. An American modeling study on the Covid-19 thus showed that a distance of one to two meters ("between 3 and 6 feet") could be enough to protect itself from droplets expelled by coughing or breathing. On the other hand, a sneeze can project postilions “up to 20 feet”, that is to say more than six meters, estimates the study carried out by the John-Hopkins University.

"At a distance of one meter, you can't escape all the projections"

The risk of contamination can also vary depending on the environment in which one finds oneself. "If I'm in a closed office with other people with ventilation on, a meter away will probably not be enough," notes the researcher. A Chinese study has shown that the air conditioning on in a restaurant in Canton "could have spread droplets" from one table to another. "We can then estimate that a meter apart, we escape a good part of the projections ... but not necessarily all," concludes Fabienne El-Khoury.

Finally, the speed of the movements made is another criterion to take into account. In France, the Ministry of Health recommends a distance not of one meter, but "of 10 m minimum between two people" during a bike ride or a jog. The government thus followed the opinion of the High Council of Public Health (HCSP) which indicated on April 24 that "physical activities contribute to a high risk of respiratory transmission by sustained ventilation (cycling, jogging) practiced closely by several people ".

Consequently, "the distance between two people practicing a sporting activity must be sufficiently increased well beyond a meter, for example 5 m for a fast walk and 10 m for the practice of jogging or a practice of the bicycle". For the time being, questions remain unanswered on how to apply and enforce these safety distances in an urban environment.

Difficult to establish a single figure

Faced with all these variables, establishing a generic figure for physical distance is complicated to say the least. “At the moment, there is no study that assures us that a 1.5 meter gap protects us radically better than a meter. But it is obvious that the farther you are from your neighbor, the less you risk being infected, ”summarizes Vincent Maréchal, professor of virology at the Sorbonne University in Paris.

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"The real problem is elsewhere: ask people to measure you a meter, they will not know. For having taken the test, most of them showed me a distance of 50 cm and two meters, ”laments the academic.

"The main thing then is not to say whether it takes a meter or a meter and a half but to insist on the fact that this distance must be respected in addition to all the other barrier gestures (washing your hands, wearing a mask etc) to limit transmission by droplets. Otherwise, it would make no sense, ”concludes the specialist.

Coronavirus: the pandemic explained by a specialist