As businesses begin to re-open, be sure to protect yourself as there are many unknowns about spreading SARS-CoV-2, the virus that causes COVID-19 disease. Here are a few of them:

What dose of SARS-CoV-2 makes a person sick?

Dr Michael Skinner, a virologist at Imperial College London, recently said: “The actual minimum number varies between different viruses and we don’t yet know what that ‘minimum infectious dose’ is for COVID-19”.

How is SARS-CoV-2 spread?

Much of the spread of SARS-CoV-2 may be through viruses being suspended in tiny particles or droplets in the air, such as mists, known as aerosols, which may be less than 1 micrometer in size. Aerosols can be spread through the following ways:

by asymptomatic individuals (i.e., those who are infected yet not showing symptoms) when breathing and speaking
by staying in the air for hours and building up within closed spaces and
by being carried further distances through air currents.

Either of these methods may cause infection if the virus gets inside the lungs, where it can replicate very rapidly, and be exhaled again before symptoms develop. One study examining 14 patients with COVID-19 found infected persons who were spreading the virus to others before they developed symptoms.

Is Six Feet Far Enough for Social Distancing?

The CDC guidelines for 6-foot social distancing are based on studies from the 1930s, before technology for detecting such small aerosols existed. Currently, little analysis has been done on transport of such small aerosols. One recent study found that SARS-CoV-2 was present in aerosols more than six feet from infected hospital patients. The effectiveness of commonly used personal protective equipment (e.g., face-masks) in slowing or preventing the transmission of SARS-CoV-2 is still not understood. For example, the N95 and surgical masks have not been tested for their effectiveness in containing aerosols emitted from a sneeze or cough which can reach speeds of 33 to 100 feet per second and travel 23 to 27 feet.

While it is unknown for certain if SARS-CoV-2 can spread through aerosols, one suggestive study found that samples taken from the air vents in hospitals contained the virus. Also, several cases of infection of persons working in hospitals housing infected patients, but who had no contact with those patients, suggest that aerosol transmission is a possibility. The study concludes, “If the aerosols can spread COVID-19, prevention and control will be much more difficult.”

Does it Spread Less Outdoors?

Few studies have been conducted on the spread of SARS-CoV-2 outside. In urban areas, viruses can attach to dust or particulates which increases the chances of them being inhaled. A recent analysis comparing COVID-19 cases in 120 Chinese cities with ambient levels of six common air pollutants found a significant statistical relationship between air pollution and infections. More studies are needed to know how the outdoors impacts the spread of the virus.

These unanswered questions about the spread of SARS-CoV-2 keep fibre: A Homespun Spa closed to prevent spread of the virus.

Many thanks to Steven Donkin for the basis of this summary.

Unanswered Questions About the Spread