COVID-19 News: Swiss Study Reveals That Asymptomatic COVID-19 Infected Individuals Can Transmit SARS-CoV-2 Just Through Normal Breathing

COVID-19 News: A new Swiss study warns  that asymptomatic carriers may transmit the SARS-CoV-2 coronavirus that causes the deadly COVID-19 disease, by merely breathing.


 
Researchers at the Swiss Centre for Occupational and Environmental Health and the University of Zurich came across the findings after wanting to estimate virus release from non-symptomatic carriers into different aerosol sizes by coughing and normal breathing and also to observe what exposure can result from these activities in a room shared with other people.
 
So far medical experts have found that the virus may cause severe disease in around 20 percent of those infected. Majority other patients may only experience mild to moderate symptoms, while some are asymptomatic. This means that they do not manifest any symptoms of the viral infection at all. (the rough or approximately population that can be asymptomatic is still not yet known.)
 
Disturbingly, these asymptomatic carriers are still capable of spreading the virus, making it more difficult to contain and isolate active cases. The research findings published on the preprint server medRxiv, shows that even asymptomatic carriers can spread the virus by merely breathing in a room. https://www.medrxiv.org/content/10.1101/2020.04.27.20081398v1
 
The Swiss researchers modeled the release of viruses from individual patients by calculating the viral load per exhaled droplets formed during normal breathing and while coughing. The size distribution gave a base estimate of the concentration of the virus copes released by a regularly breathing or coughing patient. The researchers also simulated the situation when a carrier is in an enclosed room with different ventilation air exchange rates.
 
The research team  found that when they computed the viral emissions from carriers who are breathing normally, they found that the highest virus load is present in the largest aerosol size with a cumulative total emission per breath of 0.34 copes/cm3 (air) for an average patient, while 11.5 copies/cm3 for high emitters. The total emissions in the PM10 fraction were approximately one-third of these values with 0.12 copies/cm3 (average) and 4.1 copes/cm3 (high) per breath.

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The findings imply that just by merely breathing, patients can still transmit the novel coronavirus. Further, the team also calculated the virus emissions from a coughing patient. They found that the total emission per cough was about 19,400 copies/cm3 for an average patient, and 651,315 copies/cm3 for high emitters. The cumulative emissions in the PM10 fraction were half of these values, with 10,900 copies/cm 3 (average) and a staggering 366,000 copies/cm3 (high) per cough.&l t;br />  
The researchers also estimated the risk of exposure of bystanders who are spending time in the same room with a COVID-19 positive patient. This may help shed light on how the virus spreads in closed areas with asymptomatic patients who are not aware that they are carriers. The team revealed that for a typical hospital ventilation situation of ten air exchanges per hour, the concentration plateaus after about 30 minutes, while for a workplace with about three air exchanges per hour, concentrations continue to increase for almost three hours.
 
The research sheds light on how the virus behaves and how it spreads across populations via local transmission. An increased number of viruses are expected to be released by COVID-19 positive patients in the form of airborne aerosols, particularly when they are coughing. However, infected patients, even asymptomatic ones, can still transmit the virus even through normal breathing.
 
Despite a large proportion of the virus is in the form of large particles that can deposit rapidly, there are still viruses suspended in smaller size aerosols, which can remain airborne for an extended time. These smaller air particles are more potent since they can reach the deeper regions of the lungs.
 
The researchers also warned about the risk of staying in a room with a COVID-19 patient. An average person breathes about one-half m3 per hour in resting state, and it can increase during exercise.
 
The researchers stressed in their study paper, “Thus, a person spending time in a room with an average emitting patient breathing normally has a realistic chance of inhaling tens to hundreds of copies of the virus even when keeping distance from that person. The situation is worse in the presence of a high emitter and worst if the patient is a coughing high emitter.”
 
 The chances of contracting the virus is grim in the presence of a high emitter of the SARS-CoV-2 coronavirus and even worse if the patient is coughing.
 
Dr Michael Riedker from the Swiss Centre for Occupational and Environmental Health and co-author of the research told Thailand Medical News, “The very high virus load in exhaled respiratory aerosols proposed by our assessment may be an explanation why COVID-19 was associated with much more transfections to hospital staff than what was expected from SARS.”
 
It must also be noted that while mandating everyone to wear a surgical mask as effective infection control and prevention of infection, the protective factors may still be inadequate if long periods are spent in the same room with a coronavirus positive patient.
 
The medical researchers suggest that workplaces and other buildings should improve ventilation in the room. Workplaces may need to revamp designs and the number of people staying in an office. The risk of infection is real when being near an asymptomatic carrier in a room for more than a few minutes, even if social distancing is observed.
 
The researchers also stressed that sharing workplace rooms with asymptomatic carriers is not advised. Hence, the team suggests that offices should not be shared if there is no mass testing available to differentiate healthy and non-symptomatic cases. Hospitals should also provide adequate personal protective equipment (PPE)s to health workers, especially when in the same room as a patient who is coughing. All patients should wear a well-fitting surgical face mask to reduce emissions, even if they are not coughing.
 
The research findings also implies that most social distancing measures are inadequate and that testing of the general population is very critical to identify asymptomatic carriers.
 
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