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Is 6 feet enough?

Coronavirus Precautions- Is 6 feet enough?

    Many people have taken the precautions to stay inside and avoid contact with others. However, it is inevitable that one will have to go outside eventually, whether it be for groceries or a breath of fresh air. Multiple states are also in the process of reopening so many people will face some sort of social interaction in the near future. The CDC recommends that everyone stay a minimum of six feet apart when going outside to reduce transmission of the coronavirus. But is 6 feet enough to prevent infection?

How far the Virus can travel

    The distance a respiratory droplet can travel is dependent on many factors including the type of emission, temperature and humidity. Most droplets evaporate in the air with smaller droplets in warmer climates evaporating faster. A study published in JAMA, Journal of American Medical Association, shows that gas clouds from a human sneeze can travel a distance from 23-27 feet or 7-8 meters. These gas clouds have the potential to hold virus particles from COVID-19.

Bourouiba, Lydia. “Turbulent Gas Clouds and Respiratory Pathogen Emissions.” JAMA, American Medical Association, 12 May 2020, jamanetwork.com/journals/jama/fullarticle/2763852.

How much Virus is released and Time taken to Infection

    Erin Bromage, a Professor of Biology at the University of Massachusetts Dartmouth gives more information on each type of respiratory emission on her website. To summarize Bromage's main points: 

Cough: Releases about 3,000 droplets at 50 miles per hour
Sneeze: Releases about 30,000 droplets up to 200 miles per hour
Breath: Releases between 50-5000 droplets traveling at low velocity
Speaking: Releases 200 virus particles per minute

A person only needs to inhale 1,000 virus particles before being infected
Successful infection= Exposure to Virus x Time

    An infected person may contain as many as 200 million virus particles in a single cough or sneeze. These particles are easily dispersed everywhere in the surrounding environment. Even small infected particles can linger for a few minutes and fill up an entire room. All it takes is for someone to enter that room within a few minutes and take a couple breaths before they could be infected. 
    
    Respiratory droplets released from breathing contain low levels of virus particles. The amount of coronavirus particles in a breath is not known. However, influenza, releasing about 30 particles per minute, can be used as a guide. Therefore, with general breathing at 30 virus particles per minute, it takes about 33 minutes for someone to become infected (1000 virus particles/30 virus particles per minute). This is of course, assuming that every virus particle is inhaled which is extremely unlikely. Through speaking, assuming every virus particle is inhaled, it takes about 5 minutes to become infected (1000/200). 

The Bottom Line

    These studies show that it is possible for a human sneeze, containing up to 200 million virus particles, to travel up to 23-27 feet. A person only needs to inhale 1,000 of these virus particles before being infected. Additionally, it has been shown that someone can be infected from the virus within minutes after being near or in the same room as an infected person. So to answer the question, is 6 feet enough? No, 6 feet is not enough to prevent infection of COVID-19. However, maintaining this distance is better than not keeping it at all. As Matthew Meselson of Harvard University says: "It's better than two feet, and ten feet is better than six." Other studies (described in Efficacy of Masks post) have shown that masks and face shields significantly reduce the risk of infection. Although being in the same room or coming in contact with another increases risk of infection, wearing a mask and maintaining at least 6 feet can cancel out this added risk and diminish chances of infection. 

Sources

1. Bourouiba, Lydia. “Turbulent Gas Clouds and Respiratory Pathogen Emissions.” JAMA, American Medical Association, 12 May 2020, jamanetwork.com/journals/jama/fullarticle/2763852.
2. Bromage, Erin. “The Risks - Know Them - Avoid Them.” Erin Bromage PhD: 13 May 2020,www.erinbromage.com/post/the-risks-know-them-avoid-them?campaign_id=9&emc=edit_nn_20200511&instance_id=18384&nl=the-morning®i_id=104079047&segment_id=27239&te=1&user_id=a1ffb30ce1c80314068039118d254073

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