This is how you should be social distancing – depending on where you are and what you’re doing

Two-metre social distancing was born in 2020, right?

Wrong. It’s more than 100 years old and was proposed by German scientist Carl Flügge in 1897. What’s more, recent research has found that droplets from sneezes can travel up to eight metres. So is standard distancing guidance out of date?

Concern about such facts has led to a new ‘traffic light’-style chart by researchers from Oxford and MIT, published in medical journal, The BMJ.

They argue that the 1-2 metre safe distancing guidance is “an oversimplification” based on “outdated science”. Instead, they favour a more nuanced model based on context and risk. Standing silently next to someone outdoors creates a much lower chance of transmission, they say. But a long time in a noisy bar is seen as riskier.

So is it time for a rethink?

The ‘traffic light’ chart

The central idea behind the chart is that “environmental influences are complex” and require different, appropriately calibrated responses.

The chart shows that the highest risk situations (in red) are where there is ‘high occupancy’ over a prolonged period. Quiet, short, ‘low occupancy’ gatherings with just a few people outdoors are the least risky (green).

The accompanying report gives the example, in recent months, of the hundreds of workers at meat processing plants around the world who have tested positive for COVID-19.

One explanation for these high transmission rates is the difficulty of workers on fast-moving production lines to stay enough apart. Other factors include the likelihood of background noise, which can lead to shouting – dispersing infectious droplets.

“Similar compound risk situations might occur in other crowded, noisy, indoor environments, such as pubs or live music venues,” the researchers say.

For such environments, “physical distancing beyond two metres and minimizing occupancy time should be considered,” they add.

But opposite scenarios are considered far less risky – like quiet contact, in an outdoor environment for a short time. “Less stringent distancing is likely to be adequate in low-risk scenarios,” the team says.

Finding the right distance

But once you start breaking down risks into sub-categories, things get complicated. Exactly how far apart should people be?

A study in 1948 found that, among a group of people with haemolytic streptococci infections, some of the bacteria from sneezing managed to spread almost 2.9 metres. But most of the participants produced large droplets that struggled to get beyond two metres. In other words – we are all different.

Yet policymakers need to find a response that works in the best way for the greatest number of people. And in the past, the majority experience has prevailed. So shouldn’t we just stick with 1-2 metres?

It’s complicated

No, say the report’s authors, who think the 1-2 metre view is outdated. They cite research showing eight out of 10 recent studies into “horizontal projection of respiratory droplets” (like sneezing) have found that particles can travel more than two metres and in some cases up to eight.

At the same time, scientists are becoming increasingly aware that airflow and ventilation is also a major factor in transmission. Without much airflow, droplets tend not to get far. But airflow patterns also pose a risk.

In a restaurant in China, 10 people within three separate families were infected with COVID-19 in an hour, even though they were sat at least two metres apart.

Complexities like this guide the report’s overall recommendation that rules on distancing should “reflect the multiple factors that affect risk, including ventilation, occupancy, and exposure time”.

As the chart shows, it isn’t really possible to create a distance that works for everyone, because every situation is different.

In low-risk scenarios, the researchers say, a little less caution is likely to be safe. But when we’re in ‘red’ high-risk territory, we probably need to raise our guard.