Is 2m a Safe Social Distance for Coronavirus?

Check out this answer from Consensus:

Maintaining a distance of 2 meters is generally supported by public health authorities and research as an effective measure to reduce the transmission of COVID-19. While this distance significantly lowers the risk of infection, it is not foolproof, especially in environments with poor ventilation. Therefore, combining physical distancing with other preventive measures such as mask-wearing and proper ventilation is crucial for optimal protection.

The COVID-19 pandemic has necessitated the implementation of various public health measures to curb the spread of the virus. One of the most widely recommended measures is maintaining a physical distance between individuals. This synthesis examines whether maintaining a distance of 2 meters (2m) is considered safe for preventing the transmission of the coronavirus.

Key Insights

• Effectiveness of Physical Distancing:
  • Maintaining a distance of 1 meter or more significantly reduces the transmission of viruses, including SARS-CoV-2, with increased protection as the distance is lengthened2 5.
  • A safe social distance can range from 1.6 to 3 meters when considering aerosol transmission of large droplets from talking, and up to 8.2 meters in calm air environments3.
• Support for 2m Distance:
  • Public health authorities recommend a 2-meter distance as a safe measure to reduce COVID-19 transmission, emphasizing the importance of spatial distancing along with social support1.
  • The practice of maintaining a distance of 1 to 2 meters is widely recommended to slow or halt the spread of COVID-19, especially in high-risk settings like orthodontic practices4.
• Impact on Transmission Rates:
  • Social distancing policies, including maintaining physical distance, have been effective in slowing the spread of COVID-19, as evidenced by reduced infection rates in areas with strict distancing measures5 6.
• Consideration of Bioaerosol Transmission:
  • Even at a distance of 2 meters, there is a potential risk of exposure to submicron particles that can remain viable in the air for hours, suggesting that while 2 meters is beneficial, it may not completely eliminate the risk of transmission in stagnant air environments8.

Is 2m a safe social distance for coronavirus?

David Hui has answered Likely

An expert from City University of Hong Kong in Infectious diseases

Yes respiratory droplets can travel between 1 to 1.8m. Thus 2m is a safe distance.

However, the 2m distance alone does not help in crowded cities. Keeping a safe distance alone would not be effective in crowded cities such as Hong Kong. There is simply no room to move in a packed train station, inside the train/bus or in a busy shopping mall or restaurant when someone coughs or sneezes.

In Hong Kong we would recommend wearing a surgical mask and regular hand hygiene when travelling by public transport or walking in crowded areas.

Is 2m a safe social distance for coronavirus?

Jane Heffernan has answered Likely

An expert from University of York in Infectious diseases, Epidemiology

The 2m (6ft) rule comes from sputum droplet knowledge. Coughs and sneezes expel droplets that can travel certain distances. The 2m (6ft) guideline tries to ensure that people are not exposed to droplets that may carry infectious doses of COVID-19.

Is 2m a safe social distance for coronavirus?

Philip Russo has answered Likely

An expert from Monash University in Nursing, Infectious diseases

The coronavirus is spread from person to person when someone with the virus coughs or sneezes. So people in close contact are at high risk.

Respiratory droplets can land in your mouth or nose. Alternatively, droplets could land on your face, and the next time you touch your face, and then rub your eye, you could infect yourself.

We know the influenza virus is spread in a similar way. One study shows when healthcare workers are within 1.8 metres of patients with influenza, their risk of being infected is increased.

A quick search online will find lots of videos showing droplet expulsion from a sneeze. But there is a lack of good evidence to know for sure how far infectious droplets travel, and what is a “safe” distance.

Research is often laboratory based and doesn’t automatically translate to real-life situations. Then there are the variables about the number of infectious particles; their airborne survival; the humidity; and the speed of expulsion of the “turbulent buoyant clouds” (tornadoes of germs).

The US Centers for Disease Control and Prevention advises flu can spread up to 6 feet (1.8 metres). The key message is, the closer you are, the bigger the spray.

Similar research is yet to be done on the coronavirus. But the similarity with the way influenza is spread means we can apply what we know about influenza to the coronavirus.

What do others recommend?

The recommendation of 1.5 metres is not only based on our knowledge of influenza, it is also a practical distance that allows us to go about our daily lives.

Obviously it’s not a precise measurement, nor is it absolutely guaranteed to prevent spread. But that approximate distance is better than no distance.

The lack of scientific rigour behind these recommendations is borne out in the varied advice from around the world.

The UK’s National Health Service recommends people with symptoms stay at least 2 metres away from others.

The US Centers for Disease Control and Prevention recommends everybody should “put distance between yourself and other people”.

Finally, the World Health Organisation advises to keep at least 1 metre between you and anyone coughing and sneezing.

So you get the general idea. Don’t get close.

What does this mean in practical terms?

So, how do we keep 1.5 metres apart, short of carrying around a tape measure?

It’s about two arms lengths, but don’t stress about it. A little bit less is OK, a little bit more is good.

In a nutshell

Right now, avoiding close contact with others is important, and keeping 1.5 metres away from each other is not an exact science. It’s about keeping some sensible and practical distance between you and others.

It is just one of the strategies we can easily use to help slow down the spread of this virus. And please, wash your hands, and if you have symptoms, stay at home and seek medical advice.

This answer was adapted from my answer in The Conversation.

Is 2m a safe social distance for coronavirus?

Jonathan Reid has answered Likely

An expert from Bristol University in Aerobiology, Chemistry

Physical distancing is a way of reducing the exposure of an individual to the large droplets generated when someone sneezes, coughs or even speaks. These large droplets do not remain airborne for long, they settle out falling to the ground in under 10-20 seconds. However, they are initially carried forward by the momentum of the cloud when someone sneezes, coughs or speaks at anywhere from a speed of 5 m/s to 30 m/s.

It has long been established that the droplets can be carried over a distance of 1-2 m, with the larger droplets falling out in around 1 m and the smaller droplets (similar to the diameter of a human hair) in around 2 m. So, the further you stand away from someone, the smaller the fraction of droplets you are exposed to when someone sneezes or coughs in your direction, and the less likely you are to come into contact with the virus.

Is there a strict cut-off in terms of effectiveness?

No, it is just a matter of reducing risk with increased physical distance. The further you stand away from someone, the fewer droplets you will be exposed to when someone sneezes or coughs in your direction. 1 m only prevents you from being exposed to the largest of droplets, 2 m reduces your exposure but doesn’t make it zero risk. In fact, droplets smaller than the diameter of a human hair can be carried over more than 2 m, and the very smallest droplets, often referred to as aerosols, can remain airborne for minutes or hours in a room and travel over larger distances. The distances travelled also depend on the temperature and humidity, and if there are air currents, e.g. a breeze outside or a fan inside. So, the guidelines on physical distances are not strict cut-offs, they are just guidance and recognise that the distance the droplets are carried depends on a number of factors.

At the moment, we don’t know how much virus these droplets carry and how long the virus survives for when it is in these droplets and aerosols. We also don’t know how much virus someone needs to be exposed to to get COVID-19 and this also then depends on how long they may be near someone. So assessing risk is difficult and, just as with face masks, it makes sense to be cautious until we have more information if the goal is to minimise the spread of the virus, a larger distance will lead to reduced risk on a population scale.

This answer was adapted from my original quote at the Science Media Centre.