Watch Live: CityNews at Six Vancouver

Physical distance of two metres likely not enough to prevent spread of coronavirus, experts suggest

VANCOUVER (NEWS 1130) – You’ve been told to keep at least two metres – or six feet – from others countless times over the last few months, but it looks like that may not be enough.

Writing in Science Magazine, three experts from universities in Taiwan and California say unlike traditional respiratory diseases, which are often transmitted through droplets from infected people as they sneeze or cough, a large proportion of the spread of COVID-19 appears to be happening through airborne transmission of aerosols produced by asymptomatic people as they breathe or speak.

“Increasing evidence for SARS-CoV-2 suggests the 6 ft WHO recommendation is likely not enough under many indoor conditions where aerosols can remain airborne for hours, accumulate over time, and follow air flows over distances further than 6 ft,” the commentary by Kimberly A. Prather, Chia C. Wang, and Robert T. Schooley reads.

“Respiratory droplets will undergo gravitational settling faster than they evaporate, contaminating surfaces and leading to contact transmission. Smaller aerosols (=5 µm) will evaporate faster than they can settle, are buoyant, and thus can be affected by air currents, which can transport them over longer distances.”

Those aerosols, they say, can accumulate, remain infectious in indoor air for hours, and be easily inhaled deep into the lungs, allowing transmission regardless of physical distancing. They even point to a study in hospitals in Wuhan, China, which found the COVID-19 virus in aerosols more than two metres from patients.

The experts add the World Health Organization recommendations for social distancing of six feet and hand washing to reduce the spread of the coronavirus are based on studies of respiratory droplets — not aerosol transmission — carried out in the 1930s.

So what is the magic number for physical distancing? They say given how little is known about the production and airborne behavior of infectious respiratory droplets, it is difficult to define a safe distance.

However, they believe a good comparison is exhaled cigarette smoke.

“The distance from a smoker at which one smells cigarette smoke indicates the distance in those surroundings at which one could inhale infectious aerosols,” the experts write. “In an enclosed room with asymptomatic individuals, infectious aerosol concentrations can increase over time. Overall, the probability of becoming infected indoors will depend on the total amount of SARS-CoV-2 inhaled.”

The experts argue for society to resume, measures to limit aerosol transmission must be implemented, including universal masking and regular, widespread testing to identify and isolate infected asymptomatic individuals, rather than physical distancing.

“Masks provide a critical barrier, reducing the number of infectious viruses in exhaled breath, especially of asymptomatic people and those with mild symptoms,” they write, adding it’s especially important to wear masks in places where high concentrations of the coronavirus can accumulate in, like “health care settings, airplanes, restaurants, and other crowded places with reduced ventilation.”

Top Stories

Top Stories

Most Watched Today