Coronavirus

The Center for Disease and Control and Prevention (CDC) recommends  6-feet social distancing between people. But this might not prevent the spreading of the virus.

A study published by the Journal of American Medical Association determined that liquid droplets (the way the novel coronavirus is spread) from sneezing, coughing and exhaling, under the right conditions, can travel more than 26 feet and stay in the air for minutes.

The CDC this month recommended that ALL Americans wearing non-surgical face masks in public, and it’s especially important to wear in places that social distancing is hard to maintain.

“There is no virtual wall at this 3- to 6-feet distance,” says Lydia Bourouiba, the study’s author, who specializes in fluid dynamics and is an associate professor at the Massachusetts Institute of Technology. The healthcare workers that work with infected patience have the greatest risk.

This study looked at turbulent gas. Turbulent gases are the gas emitted when someone sneezes, coughs, or exhales. Some liquid droplets drop onto surfaces; others can be trapped in the gases and move around with the virus-infected droplets.

There are many factors that determine how far the gas and droplets are able to travel: a person’s physiology, environment, temperature, and humidity. Typically a cough cloud can travel up to 26 feet, and a cough can reach 16 to 19 feet. These droplets are very small and invisible.

According to the World Health Organization, a cough can produce 3,000 droplets, and a sneeze can produce 40,000 droplets.

“Aerosols are different,” says Dr. Stanley Deresinski, clinical professor of medicine and infectious diseases at Stanford University. “Very small particles may be suspended in the air for a long time, sometimes for hours. They’re suspended by air currents.”

These floating aerosols can stay suspending into the air for long enough for someone to walk through and be infected by the virus.

The virus could potentially be detected in air condition systems inside the building.

A JAMA Network study found that exhaust outlets tested positive for SARS-CoV-2: “small virus-laden droplets may be displaced by airflows and deposited on equipment such as vents,” the study says.

“Now, there are other questions about whether the detected virus particles are still live,” says Bourouiba. “However, finding the virus in air vents is more compatible with that longer distance range that can be reached through the cloud.” It is not known whether the viruses are still alive though.

The best defense is the outdoors and opening the windows, which dissipate the cloud droplets.

Surgical masks are helpful, but they do not help with protecting from inhaling smaller airborne particles. N95 respirator filters out 95% of airborne particles. It reduces the aerosol concentration to 1/10 of that in the room.

An elastomeric respirator is a reusable device with exchangeable cartridge filters. This works as well at the N95 respirator.

With the CDC recommending the general public wearing masks, Bourouiba stated the following “The efficacy of those homemade solutions need to be quantified. Exhalations or violent exhalations such as coughs or sneezes would be deflected to the sides of these masks — as they are not perfectly sealed. Flow follows the path of least resistance. The benefit of these masks is that the cloud deflection and impact against the mask dissipate energy and thus can reduce the range of propagation of the cloud. It is important therefore to understand that such masks are not necessarily protective for the wearer in terms of preventing inhalation of the residual droplets in the air, which enter from the sides unfiltered, but they can provide a way to reduce the range of contamination from the droplets-laden cloud.”

With allergy season upon us, Bourouiba warned that people carrying COVID-19 without symptoms could spread COVID-19 through sneezing and coughing triggered by allergies.

Related: COVID-19 Worldwide Tracker
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