IS IT SAFE TO GO OUT FOR A WALK?
Worry about COVID-19 shouldn’t stop you if you’re healthy, just keep a safe distance
Bisphenol A. Aspartame. Phthalates. Perfluoroalkyl substances. Cholesterol. Vitamins. Parabens. GMOS. Food additives. Electromagnetic radiation. Pesticide residues. Plastics. Antioxidants.
These are the topics that I’ve become accustomed to dealing with over the years, but now they are not even on the back burner, they are off the stove. All the burners are occupied, boiling over with questions about the coronavirus. Droves of questions we have, answers are not so plentiful. And unfortunately, every answer comes with some degree of uncertainty since so much about infection with the SARSCOV-2 is up in the air.
Speaking about up in the air, many of you have asked about airborne transmission of the virus, especially the possibility of being infected when walking outside. A study published in the New England Journal of Medicine about the virus being airborne has raised concern, but the term “airborne” requires some clarification.
When someone coughs or sneezes, tiny droplets of mucus or saliva are expelled, and in the case of a respiratory virus infection, these droplets can harbour the virus. So, indeed, the virus can be said to be “airborne.” However, due to gravity, these droplets fall to the ground relatively quickly, usually travelling less than two metres.
Being within this radius of an infected person when they cough or sneeze does present a significant risk of infection. The droplets also pose a risk after they fall, since there is a chance of touching the contaminated surface and then conveying the virus to the face. This is why it is so important to disinfect surfaces that could have been exposed to droplets from an infected person. How long the virus remains viable depends on the type of surface. On smooth surfaces such as steel or plastic it can be days, on porous materials such as paper or fabric, around a day.
Droplets are not the only means by which a virus can travel through the air. “Aerosols” consist of extremely fine liquid or solid particles, smaller than droplets, that can be held aloft by air currents or by attraction to air molecules, thereby essentially defying gravity. If the SARSCOV-2 virus were aerosolized, infection could conceivably occur at distances greater than two metres from the infected person.
The question is whether this is a realistic possibility. The New England Journal paper reported that in some cases aerosolized virus was detected for as long as three hours after being introduced into the air, raising the possibility that an individual could be infected by walking into an invisible cloud of viral particles long after the sneezer is gone. However, in the study the virus was released from a nebulizer, a device that is designed to release extremely fine particles, and furthermore, a large viral load was used. Many researchers have questioned whether this is a real-life situation since there is some evidence to the contrary.
In Singapore, sampling of the air in the hospital room of COVID -19 patients who were symptomatic detected no aerosolized virus. There were viral deposits on surfaces, as one would expect. Researchers in China analyzed air samples in two hospitals where COVID-19 patients were being treated and found no aerosolized virus except near patients’ toilets. It seems that virus in feces was being aerosolized by flushing. If an uninfected person used that toilet, contracting the disease could in theory be possible.
Obviously, it is a good idea to close the toilet lid before flushing. The presence of the virus in feces raises the possibility of fecal-oral transmission and further underlines the critical importance of handwashing.
In this context, people have asked about the possibility of the virus being transmitted by flatulation. This is extremely unlikely since flatus is a mixture of gases and does not contain droplets. In any case, lighting the emerging wind with hopes of destroying any virus, as one adventurous correspondent suggested, is a decidedly bad idea.
Epidemiologists have also raised the point that if aerosol transmission of the virus were possible, infection rates would be much higher, particularly among household members. Neither the World Health Organization (WHO) nor the Centers for Disease Control (CDC) believe that transmission of this coronavirus via aerosol is likely.
There is one exception to this. During certain medical procedures, such as bronchoscopy, intubation of a patient, or fitting a BIPAP device to ease breathing, aerosols can be readily produced.
Any physician, as well as any nurse involved in such procedures is at risk if the patient has been infected with the coronavirus. That is why having proper protective equipment is essential. We must protect those who are protecting us.
Of course, performing such procedures is a very different situation from being out for a walk, an activity that according to experts is extremely unlikely to result in contracting COVID-19 via inhaled air.
So, when it comes to walking, the conclusion is, relax, breathe a sigh of relief and go. Just keep your distance from people who may have gathered to chat about how physical distancing advice is overblown. It is not. joe.schwarcz@mcgill.ca
Joe Schwarcz is director of Mcgill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.