Introduction to risk of infection from breathing in fine particles of the virus. This is called “ Aerosolization “ and is an important source of infection in small , not well ventilated rooms.
We have reached the awful milestone of over 100,000 deaths in the United States from COVID-19. It has become apparent that there is a mode of transmission in addition to the “6 foot droplets” that hasn’t been accounted for. There is a growing body of evidence pointing towards aerosol transmission of microscopic viral particles that can float in the air for hours. Infection is a function of concentration of viral particles and length of time exposed; it seems 10 minutes of breathing in a higher concentration of viral particles in a poorly ventilated small room, such as a small restroom or office, or an elevator is enough to become infected.
“If an individual uses a small office or restroom a few minutes before you, and had their mask off for 10 minutes or more, that could be enough time to leave an invisible cloud of microscopic aerosolized viral particles anywhere from 20 minutes to 2 hours in a small, poorly ventilated room.”
Therefore I am recommending leaving masks on when entering such a space, even if the room is not occupied. Why? If an individual uses a small office or restroom a few minutes before you, and had their mask off for 10 minutes or more, that could be enough time to leave an invisible cloud of microscopic aerosolized viral particles anywhere from 20 minutes to 2 hours in a small, poorly ventilated room. If you then enter and remove your mask, thinking you are alone, your risk of infection escalates. To compound the problem, aerosolized particles float with the air current, effected by gravity more slowly than the droplets with the “6 foot distance” we have heard so much about. These aerosolized particles, floating in the air you breathe in, can easily float around loose fitting masks or bandanas. However even a poorly fitting mask is better than no mask as lowering the viral load you breathe in will lessen the chance of infection, or at least the severity of the infection. So when entering an empty small room or restroom, instead of letting your guard down and removing your mask, that is the time to tighten the mask, open doors and ventilate small rooms, to lower the concentration of that invisible cloud of aerosolized viral particles. These recommendations are in addition to those already given. Does it seem extreme? As of this writing there are 106,195 reasons to say no, it’s not. Stay safe.
Stephen Ralph MD ABIM DipABLM BCEM (emeritus)
Killeen Texas
The Risks-Know Them-Avoid Them : Erin Bromage
SARS-CoV-2 in Aerosols:
Richard T. Ellison III, MD reviewing Liu Y et al. Nature 2020 Apr 27 Analysis of air samples from two Wuhan hospitals identified SAR-CoV-2 RNA in submicrometer aerosol samples.The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission |PNAS
We cannot keep ignoring the possibility of airborne transmission. Here’s how to address it: The Washington Post
Coronavirus Is Aerosolized Through Talking, Exhalation:
MedscapeReducing transmission of SARS-CoV-2:
Kimberly A. Prather, Science May 27, 2020