Dr. Chris Magryta: Coronavirus transmission
Published 12:00 am Sunday, April 12, 2020
By Dr. Chris Magryta
We have looked at this virus backwards and forwards over the last few weeks. Over the ensuing weeks, I am only going to post relevant quick hits related to the virus and predominantly the United States experience. I plan to continue to focus on prevention and a dispassionate analysis of the data.
1) The data as it relates to children in the United States continues to be very reassuring. From the latest MMWR CDC report, the data shows that children are mostly asymptomatic and the death rate as of April 2 for children under 18 years of age is three cases. The U.S. has a population makeup of children and teens from birth to 18 years of age at 22% or just shy of 73,000,000 young Americans. “Among 149,082 (99.6%) reported cases for which age was known, 2,572 (1.7%) were among children aged <18 years. Data were available for a small proportion of patients on many important variables, including symptoms (9.4%), underlying conditions (13%), and hospitalization status (33%). Among those with available information, 73% of pediatric patients had symptoms of fever, cough, or shortness of breath compared with 93% of adults aged 18-64 years during the same period; 5.7% of all pediatric patients, or 20% of those for whom hospitalization status was known, were hospitalized, lower than the percentages hospitalized among all adults aged 18-64 years (10%) or those with known hospitalization status (33%). Three deaths were reported among the pediatric cases included in this analysis.” (CDC MMWR Report 4/6/20)
The key here is that the ultimate negative outcome is death and thankfully, it continues to be exceedingly rare in this critical age grouping. What the emerging data is showing is that we are finally seeing some pediatric data on who is at increased risk for hospitalizations in key at risk groups: asthma, cardiovascular disease and immune dysfunction. These groups need to be extra careful in their precautionary approach to COVID disease avoidance. Touching base with your provider makes intuitive sense while being compliant with all of your current medical regimens until you speak with them about any plans moving forward in light of the emerging data. I continue to reiterate that eating an anti inflammatory whole foods diet coupled with adequate sleep and movement provides the best chance for a great outcome if one gets infected.
2) SARS2/COVID may be transmitted through aerosol droplets from breathing. That is a belief partially based on a new article from Nature Medicine from April 2 by Dr. Leung and one of the reasons behind the new mask recommendations. They measured air samples around feverish and upper respiratory infected patients and found that influenza, seasonal (common cold-like) coronavirus (not SARS or SARS2) and rhinovirus were detectable in breath based air whether there was a cough present or not. Wearing a mask significantly reduced the ability to detect the virus in the air. (Leung et. al. 2020)
Dr. Bae and colleagues performed an interesting study with SARS2/COVID patients in the journal Annals of Internal Medicine. From the article: “A petri dish … was placed approximately 20 cm from the patients’ mouths. Patients were instructed to cough five times each onto a petri dish while wearing the following sequence of masks: no mask, surgical mask, cotton mask, and again with no mask. A separate petri dish was used for each of the five coughing episodes. Mask surfaces were swabbed with aseptic Dacron swabs in the following sequence: outer surface of surgical mask, inner surface of surgical mask, outer surface of cotton mask, and inner surface of cotton mask.”
“Neither surgical nor cotton masks effectively filtered SARS-CoV-2 during coughs by infected patients. Prior evidence that surgical masks effectively filtered influenza virus informed recommendations that patients with confirmed or suspected COVID-19 should wear face masks to prevent transmission. However, the size and concentrations of SARS-CoV-2 in aerosols generated during coughing are unknown. Oberg and Brousseau demonstrated that surgical masks did not exhibit adequate filter performance against aerosols measuring 0.9, 2.0, and 3.1 μm in diameter. Lee and colleagues showed that particles 0.04 to 0.2 μm can penetrate surgical masks. The size of the SARS-CoV particle from the 2002-2004 outbreak was estimated as 0.08 to 0.14 μm; assuming that SARS-CoV-2 has a similar size, surgical masks are unlikely to effectively filter this virus.”
“Of note, we found greater contamination on the outer than the inner mask surfaces. Although it is possible that virus particles may cross from the inner to the outer surface because of the physical pressure of swabbing, we swabbed the outer surface before the inner surface. The consistent finding of virus on the outer mask surface is unlikely to have been caused by experimental error or artifact. The mask’s aerodynamic features may explain this finding. A turbulent jet due to air leakage around the mask edge could contaminate the outer surface. Alternatively, the small aerosols of SARS-CoV-2 generated during a high-velocity cough might penetrate the masks.” (Bae et. al. 2020)
This data set throws a monkey wrench into the current recommendations. It is difficult to understand how the outside of the mask was worse off. What I glean from the data so far is that we do not have a complete grasp on the effectiveness of homemade, cloth, and surgical mask protection. The higher quality aerosol controlling N95 masks appear to work very well. That being said, it appears that wearing any mask may have two apparent benefits now: 1) decrease of self induced viral transmission from touching an infected surface and then touching a mucous membrane on your face, 2) decrease but not stopping aerosol droplet spread whether you are asymptomatic or symptomatic.
Touching the outside of a mask if you are ill will offer a contamination event since the virus is found on the outside after a cough and now you have viral particles on your fingers. This is also a reason to change masks daily or even more frequently in a healthcare setting when exposed to ill individuals.
What is the take home point from this murky data: I think that wearing a mask makes prudent sense for the reasons stated above if you are not ill and you are planning on going out into society. If you have any COVID symptoms at all, stay home if you do not need to be seen by a physician and don’t rely on this mechanism for complete protection as it is not and never will be. Hand washing frequently and avoidance of mucous membrane touching are still by far the best methods of infectious disease prevention and transmission.
Dr. Chris Magryta is a physician at Salisbury Pediatric Associates. Contact him at firstname.lastname@example.org