SHOTLIST:

1. Various of people on the streets
2. Various people standing in line respecting the distance
3. Various of people in train stations
4. Various of temperature controls
5. Various of people on the streets
6. Various of people in shops

STORYLINE:

Experts may be re-evaluating social distancing guidelines, amid mounting evidence that the new coronavirus could travel beyond two meters in certain circumstances.

In a new study, published this week in the BMJ and cited by the Washington Post, a team of infectious disease experts argued that protocols from two meters apart (six feet, which is equivalent to 1.80 meters) are too rigid. and they are based on old science and observations based on other viruses.

Indeed, factors such as air circulation, ventilation, exposure time, crowd density, whether people wear face masks and whether they are silent, talking, shouting or singing should be part of the assessment of whether the social distance is sufficient.

"I think six feet is a good number, but we have to convey that this is a starting point," Linsey Marr, a Virginia Tech professor of civil and environmental engineering, who studies viruses transmitted by the air.

The consensus knowledge behind the two-meter distance arose from the research of a German biologist, Carl Flügge, who in the late 1800s suggested that it was the farthest microbe-containing droplets could travel. Unfortunately, her hypothesis overlooked further particles invisible to the naked eye; in particular, the tiny droplets of body fluids and viruses that float in the air as aerosols.

If the new coronavirus can float in the air as vapor, what has been believed until now about distances to avoid contagion is inappropriate.

And, while airborne transmission has yet to be conclusively proven, a growing number of experts believe there is sufficient evidence of super-spread events in which the virus has been transmitted to people many meters away from the source of infection.

In a well-studied choir practice that took place in Washington state in March, a singer transmitted the coronavirus to 52 people, causing the infection to have reached a person almost 14 meters away.

The World Health Organization (WHO), for its part, has recommended at least one meter, while some European countries establish social distances of 1.5 meters, others two meters, and some even more than two meters.

Because public health officials in the United States insisted so much with the two meters of distance, the measures have been confused with a goal within which there is complete security of non-contagion.

Another key factor is air movement. “It becomes very important not to think only of a fixed distance. You need to think about air flow, "said Lydia Bourouiba, author of the aforementioned BMJ report, who studies the fluid dynamics of infectious diseases at the Massachusetts Institute of Technology.

A useful analogy is the cloud of a cigarette smoker. "As you move away, you are exposed to less because it becomes more diluted," Marr said. "However, the smoke doesn't stop at six feet," he added.

Bourouiba also assured that the time to which one is exposed to the virus is a determining factor, although it is not clear how long a non-risky encounter would last. "Some speak for five to 15 minutes, but there is not enough science yet to determine that," he said.