Two-metre social distancing rule may not stop COVID-19 transmission, warn experts
According to the study, a light wind can carry infected droplets three times further in just five seconds. Experts also warn that shorter adults and children could be at higher risk if they are within the trajectory of droplets carrying the infection.
As several countries in the world have begun to ease lockdown restrictions amid the coronavirus pandemic, scientists in a new study have warned that the “broadly accepted” two metre or six feet social distancing rule may not be enough to stop the spread of the highly-contagious virus. Experts say that just a light wind can transmit infected droplets between people while outdoors.
The study, published in Physics of Fluids journal, may force public health officials in several countries to reconsider their safety guidelines for keeping COVID-19 -- the deadly disease caused by the new coronavirus -- at bay.
So far, at least 328,000 deaths have been recorded worldwide, according to a Johns Hopkins University tally. At least five million cases of COVID-19 have been reported across the world.
Authors Talib Dbouk and Dimitris Drikakis, from the University of Nicosia in Cyprus, discovered that two metres was a safe approximate distance in still conditions, with droplets taking about 15 seconds to fall below human waist level.
However, they found that “when a person coughs, the wind speed in an open space environment significantly influences the distance that airborne disease-carrier droplets travel”.
Experts used a computational fluid dynamics model to compare the distance travelled by human saliva droplets in different wind conditions and found that droplets could reach as far away as six metres (18 feet) in five seconds at a wind speed of just 4 km per hour. At 15 km per hour, the wind can carry droplets the same distance in just 1.6 seconds.
The researchers stated: “Our findings imply that, depending on the environmental conditions, the 2-metre social distance may not suffice.” The study added that further research was necessary into the influence of other parameters, such as relative humidity and temperature of the environment.
There are a wide range of guidelines on social distancing that differ from country to country. The World Health Organisation recommends a one metre distance between two people from separate households.
The agency says: “When someone coughs, sneezes, or speaks they spray small liquid droplets from their nose or mouth which may contain virus. If you are too close, you can breathe in the droplets, including the COVID-19 virus if the person has the disease.”
But other countries have taken advice from their own health experts and social distancing varies from two metres to one metre.
According to the BBC, the two metre rule can be traced back to research in the 1930s that showed droplets of liquid from coughs or sneezes would land within a one-two metre range.
Experts also warned that shorter adults and children could be at higher risk if they were within the trajectory of droplets carrying the infection.