Scarcity of Aerosolized Viruses
How often have government officials acknowledged that people can contract a virus through the air? Think about it. An unmasked individual has a phone conversation in a room before leaving. Then you enter the same room and contract a virus.
How many times has the world been warned that a public virus can aerosolize like this? As is the case with ebola, it is more common to say that contact with bodily fluids results in contamination. Another distinction is short-distance airborne droplets.
The spread of virus through a microscopic mist in the air has been a topic of contentious debate for hundreds of years. The measles and tuberculosis have been recognized by the Centers For Disease Control and Prevention (CDC) as airborne viruses. Among others, whooping cough (pertussis) and influenza, make the list. The novel coronavirus may soon be on the CDC list of airborne viruses with the further distinction of aerosolized transmission.
WHO Versus CDC
The World Health Organization (WHO) provides global health guidance on communicable diseases. The CDC is one of the major operating components of the United States Department of Health and Human Services. Both organizations should be harmonious in their messaging. Sometimes they differ and at other times they reach the same conclusions.
Transmission of COVID-19 is primarily occurring from people when they have symptoms. It can also happen just prior to developing symptoms. Pre-symptomatic refers to infected people who have not yet manifest symptoms but who develop symptoms later. Asymptomatic refers to infected people that never develop symptoms during the period of infection.
WHO, together with the scientific community, has been actively discussing and evaluating whether SARS-CoV-2 [COVID-19] may also spread through aerosols in the absence of aerosol generating procedures, particularly in indoor settings with poor ventilation. —WHO
The WHO recognizes that evidence suggests COVID-19 is an aerosol virus. Current guidance indicates that COVID-19 spreads between people through direct and indirect (contaminated objects or surfaces) after days or hours. The virus half-life is a relatively short six hours, meaning that every six hours 50% of the virus shrivels up and becomes inactive or noninfectious. COVID-19 thrives best when moist and within a human host.
Spread By Surface, Droplet, or Aerosol
Communicating clear guidance nationwide or worldwide is challenging. It can take weeks, months, or longer for widespread compliance. Altering instructions leads to confusion. Many institutions have modified sanitation methods to address the spread of virus from contact with surfaces. People have been in fear of packages arriving through the mail with the potential to infect. Prepare yourself for an adjustment in transmission priority.
Emanuel Goldman notes that early tests of coronavirus survival rates conducted by H F Rabenau, et al. (2005) and Shu-Ming Duan, et al. (2003) may not represent real-world examples during the COVID-19 pandemic.
The duration in these prior studies was based on the equivalent of 100 infected people (between 106 to 107 infectious virus particles) coughing and sneezing directly on a small non-porous surface area. One or two persons coughing on a surface with a six-hour half life leaves significantly less residual contaminate after a day than 100 people.
Between surface and aerosol transmission, more attention is focusing on aerosol. Aerosolization occurs when people sing, shout, or talk. Larger groups transmit a higher concentration of aerosol. We have been primarily avoiding people in close contact with an infected person. COVID-19 droplets can get into your mouth, nose, or eyes of infectious persons within 1 meter. So we double or triple that distance to be safe. With aerosolization, this distance is grossly understated.
A New Priority
Prioritization has been until now: (1) one-meter airborne droplets, (2) contaminated surfaces. We are now moving toward a new prioritization of: (1) aerosolization, (2) one-meter airborne droplets, (3) contaminated surfaces. Aerosolization is the process or act of converting some physical substance into the form of particles small and light enough to be carried on the air into an aerosol.
The aerosol transmission warning takes precaution to a whole new level. Most people recognize that standing within close proximity of a person with a contagious disease puts you within range of projectile virus droplets. We have made the transition to accepting that someone may be either pre-symptomatic or asymptomatic. So wearing masks is a logical precaution.
But how do you warn people that air, in the absence of people, may be contagious? What precautions do you take? Here is the difference between a droplet and aerosol.
|Virus-filled particle of breath or spittle that comes out of the nose or mouth of an infected individual when they breathe, speak, cough, or sneeze. Droplets generally fall to the ground within a few feet of the person who expels them.||Microscopic virus particle that’s also expelled from an infected person's mouth when breathing, speaking, coughing, or sneezing. Smaller than droplets, aerosol particles can remain suspended in the air.|
There is concern that you can remove your mask within a communal room when no one is around and become infected. Just prior to the weekend, on September 18, 2020, the CDC updated its website by saying the virus can be transmitted through the air within enclosed spaces. As soon as the weekend was over, the CDC made a retraction, saying the notification was premature language.
“There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 6 feet (for example, during choir practice, in restaurants, or in fitness classes). In general, indoor environments without good ventilation increase this risk.” —CDC retracted September 18 post
The CDC now warns that contact within 6 feet of a COVID-19 positive individual for a cumulative 15 minutes or more within a 24-hour period can cause infection. This apparently happened to a correctional officer even though he wore a face covering during 22 interactions totaling 17 minutes within 24 hours.
Obviously, when you consider health care workers on the frontline, the type of mask and other personal protective equipment (PPE) makes a difference. Some masks are designed for breathability while others are manufactured for fine filtration. Also recognize that the virus can your the eyes, hence medical professionals wear several layers of PPE.
Whatever the final CDC wording is, you can protect yourself and loved ones by following basic precautions. Remember, infected people can transmit the virus whether they have symptoms or not. This is why it is always important to stay at least 6 feet (2 meters) from others; cover your mouth when you cough or sneeze into a bent elbow or tissue; wash hands regularly, and remain at home if you become unwell. In areas where the law mandates or there is widespread transmission, it is also imperative to wear a mask.
Researchers generally agree that proper size air filtration systems, like those with High Efficiency Particulate Air (HEPA) filters, can help reduce the concentration of aerosols within a room as long the filters are regularly replaced. Dispose of contaminated filters responsibly. Air filtration is not a guarantee against the virus but it adds another layer of protection for indoor spaces.
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- The Most Likely Way You’ll Get Infected With Covid-19. medium.com
- Dr. van Doremalen, Mr. Bushmaker, and Mr. Morris. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. N Engl J Med 2020; 382:1564-1567 DOI: 10.1056/NEJMc2004973
- Goldman E. Exaggerated risk of transmission of COVID–19 by fomites [published correction appears in Lancet Infect Dis. 2020 Jul 30;:]. Lancet Infect Dis. 2020;20(8):892-893. doi:10.1016/S1473-3099(20)30561-2
- Pringle JC, Leikauskas J, Ransom-Kelley S, et al. COVID–19 in a Correctional Facility Employee Following Multiple Brief Exposures to Persons with COVID–19—Vermont, July–August 2020. MMWR Morb Mortal Wkly Rep. ePub: 21 October 2020.
- Aerosols, Droplets, Fomites: What We Know About Transmission of COVID-19. npr.org
- CDC Publishes—Then Withdraws—Guidance On Aerosol Spread of Coronavirus. npr.org
- Scientific Brief: SARS-CoV-2 and Potential Airborne Transmission. cdc.gov
- CDC reverses statement on airborne transmission of coronavirus, says draft accidentally published. washingtonpost.com
- No matter what the CDC says, here’s why many scientists think the coronavirus is airborne. washingtonpost.com
- Cleveland Clinic Coronavirus Video. twitter.com
- Main photo by Edward Jenner from Pexels.