A single breath can transmit COVID-19

  • Simple breathing can spread COVID-19 from individuals who appear well.
  • The easy transmission of this virus changes how we will try to limit the pandemic.

Reports are emerging that even regular breathing can transmit COVID-19. The virus appears to be in expired air from people who are just breathing normally. This is very different from SARS or from other coronavirus infections where coughing is necessary. How has this happened?

Interaction of Spike Protein of COVID with cellular receptor ACE2. Science Magazine.

As I blogged a few days ago, COVID-19 has evolved very quickly in humans. COVID-19 binds to receptors on respiratory cells much stronger than SARS. This allows the virus to replicate in the nose and the throat as compared to only being produced in the lungs with SARS.

With SARS, therefore, one needs to cough to aerosol the virus and infect others because the virus is only present deep in the lung. In contrast, with COVID–19 the virus is present and replicating in the nose and throat; this means simple breathing will flush it out into the air to infect others.

It is a remarkable bit of evolution on the part of the virus; this allows the virus to increase the infection of the human population by having otherwise healthy people, who have no cough or obvious symptoms, transmit the virus. The world-wide pandemic is a direct result of the increased infectivity of COVID-19.

COVID-19 efficient transmission may result in an excess of mortality estimates for some flu pandemics.

We must remember people who are healthy and don’t have a cough can still transmit COVID-19. Since approximately 20 to 40%of COVID-19 infected individuals don’t display symptoms and patients also are able to spread the infection early on before they become sick, almost anyone can infect you.  

There are two important implications from this.

Everyone should wear a mask of some sort. These masks will capture your breathing and prevent the virus in your breath from infecting other people. Remember, wearing a mask is not to protect yourself but to protect others from your asymptomatic spread of the virus.

Virus testing won’t help at this point.  The criteria for virus testing exclude people without symptoms and will not prevent their spread of the virus at this time. Since asymptomatic people are probably a common source of infection, doing screening for virus may help identify those who need to be hospitalized but won’t prevent spread by asymptomatic individuals.

Therefore, at this point in time we should focus on masks and not viral screening as a means to limit the COVID-19 pandemic.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

6 thoughts on “A single breath can transmit COVID-19

  1. This comment confused me: “Remember, wearing a mask is not to protect yourself but to protect others from your asymptomatic spread of the virus.” If someone without Covid wears a mask, won’t that also help to protect them from breathing in the virus from the aerosols of others? If so, then they should be worn both to protect others, and also ourselves.


  2. Jim 1. shouldn’t our govt infectious disease experts have figured this out weeks ago? 2. regardless, considering that every time somebody breathes, let alone coughs,  they’re expelling from their lungs, is the newsworthiness of this that adding dangerous expulsion from the nose doubles the risk and cements the case for wearing some kind of mask to help protect others?


  3. how about you post links to your claims such as other sars not being spread by breathing?

    because it is.

    you truly believe sars and mers were only spread by coughing?

    peddling misinformation.


  4. Yes — here in the UK social distancing of a minimum of 2 metres is taken very seriously — but it was implemented too late. Our Prime Minister Boris Johnson is currently paying the price for his own policies. We are also told that the virus lives on cardboard and paper as well as plastic, possibly fo rum to 4 days — so handling packets and other objects is also spreading Covid-19. It is likely we cannot avoid coming into contact with CV-19 if we live in a community where it is active.

    The most important additional safeguard to social distancing and hand washing is to boost your own immune system. Eat well — avoid junk foods including sugar. Many believe that the usual immune boosting supplements will help here: high dose Vit C, Vit D with vit K, zinc, and iron. Take quality products and read up on what doses might be right for you. You are unlikely to do yourself any harm — excess Vit C is excreted, so you can take mega doses. Vit C has been really important in protecting against the related Ebola virus — as Ebola depletes Vit C and one cause of Ebola death was severe scurvy.


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