• Current COVID-19 social distancing rules are too rigid and need to reflect real-life risks better, say Oxford and MIT researchers.
  • They have broken-down situations into high- and low-risk categories – including speaking and singing.
  • In some situations we should probably relax restrictions, they advise, and in others, increase them.
  • The researchers say airflow is also a major factor in dispersing infectious droplets carrying the virus.

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 So is standard distancing guidance out of date?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They argue that the 1-2 metre safe distancing guidance is “an oversimplification” based on “outdated science”.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 risk of catching COVID-19 depends on where you are and what you’re doing.
The risk of catching COVID-19 depends on where you are and what you’re doing.
Image: BMJ

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.

coronavirus, health, COVID19, pandemic

What is the World Economic Forum doing to manage emerging risks from COVID-19?

The first global pandemic in more than 100 years, COVID-19 has spread throughout the world at an unprecedented speed. At the time of writing, 4.5 million cases have been confirmed and more than 300,000 people have died due to the virus.

As countries seek to recover, some of the more long-term economic, business, environmental, societal and technological challenges and opportunities are just beginning to become visible.

To help all stakeholders – communities, governments, businesses and individuals understand the emerging risks and follow-on effects generated by the impact of the coronavirus pandemic, the World Economic Forum, in collaboration with Marsh and McLennan and Zurich Insurance Group, has launched its COVID-19 Risks Outlook: A Preliminary Mapping and its Implications - a companion for decision-makers, building on the Forum’s annual Global Risks Report.

The report reveals that the economic impact of COVID-19 is dominating companies’ risks perceptions.

Companies are invited to join the Forum’s work to help manage the identified emerging risks of COVID-19 across industries to shape a better future. Read the full COVID-19 Risks Outlook: A Preliminary Mapping and its Implications report here, and our impact story with further information.

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.

This photograph from a 1941 research paper shows how sneezes disperse droplets.
This photograph from a 1941 research paper shows how sneezes disperse droplets.
Image: BMJ/Bettmann/Getty

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?

Sneeze droplets can travel for up to eight metres.
Sneeze droplets can travel for up to eight metres.
Image: BMJ/Bourouiba2

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.